Reversible polymer

Abstract

Disclosed include a thermally reversible cross-linked polymer, a device including such a polymer, and methods of producing and / or using the polymer. An example thermally reversible cross-linked polymer includes: a polysiloxane backbone comprising pendant groups, each pendant group comprising a first Diels–Alder reactive moiety connected to the polysiloxane backbone through a urea or urethane linkage; a crosslinker comprising two or more second Diels–Alder reactive moieties complementary to the first Diels–Alder reactive moieties; and reversible crosslinks formed between the first and second Diels–Alder reactive moieties, the reversible crosslinks forming at a first temperature range and break at a second temperature range higher than the first temperature range.

Description

International Patent Application Docket No. 009062.8583.WC00 REVERSIBLE POLYMERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent document claims priority to and benefits of U.S. Provisional Application Nos. 63 / 762,564 filed on February 24, 2025 and 63 / 821 ,383 filed on June 10, 2025, both entitled “REVERSIBLE POLYMER.” The entire content of each of the above identified patent applications is incorporated by reference as part of the disclosure of this patent document.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under DE-EE0010498 awarded by the Department of Energy. The government has certain rights in the invention.TECHNICAL FIELD

[0003] This patent document relates to techniques for making and using reversible polymer for photovoltaic module recycling.BACKGROUND

[0004] There has been rapid global expansion of photovoltaic (PV) installations.BRIEF DESCRIPTION OF DRAWINGS

[0005] Figure 1 A is a schematic illustrating the reversible “zip” and “unzip” functionality of a reversibly cross-linked interlayer polymer (ReCLIP) according to some embodiments of the present technology.

[0006] Figure 1B is a schematic of ReCLIP in PV module integration, illustrating reversible cross-linking and potential insertion for facilitating delamination at end-of-life, according to some embodiments of the present technology.

[0007] Figure 2A is a schematic view of an “unzippable” PV package designed for circularity, illustrating an intact module and components recovered after dissociation, according to some embodiments of the present technology.International Patent Application Docket No. 009062.8583.WO00

[0008] Figure 2B illustrates the reversible Diels-Alder reaction used to synthesize the interlayer according to some embodiments of the present technology.

[0009] Figure 2C illustrates the incorporation of Diels-Alder cross-links into PDMS via synthesis of copolymers with complementary pendant groups according to some embodiments of the present technology.

[0010] Figure 3A shows the1H-NMR spectrum of PDMS-maleimide according to some embodiments of the present technology.

[0011] Figure 3B shows the1H-NMR NMR spectrum of the starting material APTES-DMS according to some embodiments of the present technology.

[0012] Figure 30 shows the1H-NMR spectrum of synthesized PDMS-furan according to some embodiments of the present technology.

[0013] Figures 4A and 4B are photographic demonstrations of reversible cross-linking by Diels-Alder reaction showing a solid-like gel point and easy flow at elevated temperatures according to some embodiments of the present technology.

[0014] Figure 5A shows exemplary bismaleimide cross-linking agents used to increase mechanical stiffness according to some embodiments of the present technology.

[0015] Figure 5B shows exemplary irreversible cross-links using vinyl-hydride groups for hydrosilylation according to some embodiments of the present technology.

[0016] Figure 6 shows examples of reactive end or side groups (R) that can react with EVA or the Si cell to improve interfacial adhesion according to some embodiments of the present technology.

[0017] Figure 7 illustrates opportunities for cross-linking at different temperatures using (a) a cyclopentadiene-based DA couple and (b) a pyrrole / cyclohexene-based DA couple according to some embodiments of the present technology.

[0018] Figures 8A-8D illustrate the synthesis and characterization of mechanically compliant conductive polymers including stress-strain and resistance-strain performance according to some embodiments of the present technology.

[0019] Figure 9A illustrates an experimental matrix showing multi-level humidity and thermal testing conditions applied over time according to some embodiments of the present technology.International Patent Application Docket No. 009062.8583.WO00

[0020] Figure 9B shows module architectures for tested glass-glass and glass-backsheet configurations.

[0021] Figure 9C illustrates a characterization approach using photoluminescence current-voltage (PLIV) imaging and water reflectometry.

[0022] Figure 9D shows normalized PCE as a function of time for modules under varying environmental stressors.

[0023] Figure 10 shows the range of adhesion strengths at EVA interfaces reported in scientific literature.

[0024] Figure 11 shows the distribution of hot spot temperatures reported in research literature.

[0025] Figure 12 shows a synthesis of ReCLIP from commercially available starting materials according to some embodiments of the present technology.

[0026] Figure 13 shows an optimized lot of furfuryl-PDMS and its corresponding $A1 $H-NMR spectrum alongside images of previous lots according to some embodiments of the present technology.

[0027] Figure 14 shows1H-NMR spectra demonstrating reproducible conversion of target groups to ReCLIP-ready F-PDMS according to some embodiments of the present technology.

[0028] Figure 15A illustrates how furan conversion is determined via1H-NMR for precrosslinked and crosslinked states according to some embodiments of the present technology.

[0029] Figure 15B shows the forward cross-linking of F-PDMS to bismaleimide as a function of time at 60°C according to some embodiments of the present technology.

[0030] Figure 15C shows the de-crosslinking reaction as a function of time monitored by1H-NMR according to some embodiments of the present technology.

[0031] Figure 16 shows furan conversion achieved across three batches of crosslinked ReCLIP to demonstrate batch-to-batch consistency according to some embodiments of the present technology.

[0032] Figure 17A is a calibration curve relating nominal Mal:Fur ratio to actual ratios based on1H-NMR to identify the optically clear regime according to some embodiments of the present technology.International Patent Application Docket No. 009062.8583.WC00

[0033] Figure 17B is a calibration curve identifying the stoichiometric 1 :1 Mal:Fur ratio according to some embodiments of the present technology.

[0034] Figure 18 shows exemplary encapsulants, cells, glass, and equipment used for module packaging according to some embodiments of the present technology.

[0035] Figures 19A-19C show a laminator, the preparation of a mini-module, and a completed mini-module laminate according to some embodiments of the present technology.

[0036] Figures 20A-20C are schematics of 90° peel test sample stacks for different interface configurations according to some embodiments of the present technology.

[0037] Figure 21 A presents representative peel strength curves for Cell / EVA and Glass / ReCLIP-EVA interfaces according to some embodiments of the present technology.

[0038] Figure 21 B is a bar chart comparing average peel strengths of module interfaces according to some embodiments of the present technology.

[0039] Figure 22 is a comparison of shear force sustained for ReCLIP in the crosslinked state versus the de-crosslinked state according to some embodiments of the present technology.

[0040] Figure 23A shows a comparison of AM1 ,5G-weighted absorbance between standard and ReCLIP-enhanced laminates according to some embodiments of the present technology.

[0041] Figure 23B illustrates transmittance spectra comparison across laminate configurations according to some embodiments of the present technology.

[0042] Figure 24 shows an exemplary synthetic scheme for the formation of ReCLIP (compound 5) with highlighting of furan, maleimide, and urea motifs according to some embodiments of the present technology.

[0043] Figure 25A shows the1H-NMR spectrum and skeletal structure of the ReCLIP precursor (compound 3) according to some embodiments of the present technology.

[0044] Figure 25B shows a photograph of synthesized ReCLIP precursor according to some embodiments of the present technology.

[0045] Figure 26 is the full1H-NMR spectrum of furan-functionalized PDMS highlighting methyl protons and impurity peaks according to some embodiments of the present technology.International Patent Application Docket No. 009062.8583.WO00

[0046] Figure 27 shows1H-NMR spectra and visual appearance of compounds 1 and 4 after and before distillation according to some embodiments of the present technology.

[0047] Figure 28 provides a visual progress of the urea formation reaction and liquidliquid extraction process according to some embodiments of the present technology.

[0048] Figures 29A and 29B show ATR-FTIR spectra for precursors and the DA adduct according to some embodiments of the present technology.

[0049]

[0045] Figure 30 shows GPC traces indicating the functionalization reaction is nondestructive to the PDMS backbone according to some embodiments of the present technology.

[0050] Figure 31 shows13C-NMR results for structural verification of furan-functionalized PDMS and ReCLIP according to some embodiments of the present technology.

[0051] Figures 32A-32F present 1 D and 2D1H-NMR analyses to distinguish between endo and exo diastereomeric adduct configurations according to some embodiments of the present technology.

[0052] Figure 33 provides equations for quantitative determination of conversion and exo content alongside stacked NMR spectra over time according to some embodiments of the present technology.

[0053] Figure 34 presents thermogravimetric analysis (TGA) of the individual components used in the crosslinked material according to some embodiments of the present technology.

[0054] Figure 35A is a calibration curve relating bismaleimide weight percentage to actual MakFur ratio according to some embodiments of the present technology.

[0055] Figure 35B shows an array of ReCLIP formulations with varying bismaleimide content according to some embodiments of the present technology.

[0056] Figure 36A shows an example of a cured glass-ReCLIP-glass stack prior to testing according to some embodiments of the present technology.

[0057] Figure 36B provides a schematic diagram of the lap-shear geometry used for mechanical testing according to some embodiments of the present technology.International Patent Application Docket No. 009062.8583.WO00

[0058] Figures 37A-37I show time-dependent conversion and optical transparency of ReCLIP prepared at different temperatures according to some embodiments of the present technology.

[0059] Figures 38A-38C show ReCLIP cured at 50°C and then at 80°C tracked according to some embodiments of the present technology.

[0060] Figure 39 shows ReCLIP’s exo proportion based on $A1$H-NMR after curing at various temperatures according to some embodiments of the present technology.

[0061] Figures 40A and 40B show temperature-dependent de-cross-linking behavior according to some embodiments of the present technology.

[0062] Figures 41A-41 B demonstrate shear strength development and UV-Vis-NIR transmittance for ReCLIP adhesive according to some embodiments of the present technology.

[0063] Figure 41 C shows the exo adduct proportion over time based on furan and maleimide resonances.

[0064] Figure 41 D is a photograph of a cured stack prior to shear testing according to some embodiments of the present technology.

[0065] Figure 41 E is a photograph of a stack prepared for shear testing following a debond-rebond cycle according to some embodiments of the present technology.

[0066] Figures 42A and 42B show reaction progress kinetics for post-sheared films.

[0067] Figure 43 shows optical micrographs and photographs of fracture surfaces demonstrating failure modes according to some embodiments of the present technology.

[0068] Figures 44A-44C show transmittance comparisons between glass stacks and ReCLIP laminates according to some embodiments of the present technology.

[0069] Figures 45A and 45B show peel strength results for the Glass / ReCLIP-EVA interface compared to literature benchmarks according to some embodiments of the present technology.

[0070] Figures 46A-46D show a time-lapse of the programmatic delamination process for a glass-ReCLIP-glass stack according to some embodiments of the present technology.

[0071] Figure 47 is a flowchart illustrating a process of preparing a thermally reversible cross-linked polymer, according to some embodiments of the present technology.International Patent Application Docket No. 009062.8583.WO00

[0072] Figure 48 shows a process of recycling a photovoltaic module, according to some embodiments of the present technology.DETAILED DESCRIPTIONI. Introduction

[0073] When designing a consumer device, recyclability is not usually a primary consideration. Thus, packaging and encapsulation of interior and exterior components is achieved using robust materials e.g., metals, glasses, ceramics, and adhesives bearing irreversible crosslinks. If recycling is attempted, the high value components may be liberated by incineration or destructive mechanical processing. Controlled debonding using a reversible adhesive is an approach to circumvent some of this destruction.

[0074] Electronic devices packaged using materials designed for permanence pose a significant challenge to a future circular economy. For instance, circuit boards, flat panel displays, power cords, and solar panels contain tough polymers that are easiest to remove by combustion or mechanical disintegration. Such processes impose high costs on the environment and workers in developing nations, where recycling of electronic waste is typically carried out.

[0075] Merely by way of example in the context of PV technology, circularity is a pressing challenge for PV packages. The rapid global expansion of photovoltaic (PV) installations presents significant end-of-life (EoL) challenges, with module waste expected to exceed 100 million metric tons by 2050. Current recycling technologies are limited by high energy requirements and inefficient material recovery, often made worse by the permanent adhesion of encapsulants like Ethylene Vinyl Acetate (EVA) to module components. Although thermoplastic polymer encapsulants have been explored, they have all exhibited cross-linking in realistic settings.

[0076] The challenge of designing electronic assemblies amenable to responsible end-of-life separation underscores the need for reversible adhesives. These materials, if they can have the properties — e.g., electrical insulation, ease of processing, and cost — of incumbent materials, may enable facile repair, upgrades, and recycling at the end of the product’s life. Unlike conventional adhesives, which bond permanently, reversible adhesives bond strongly during normal use but debond upon application of a specificInternational Patent Application Docket No. 009062.8583.WO00 stimulus (e.g., heat, ultrasound, or UV light). As such, reversible adhesives can facilitate applications spanning consumer electronics (e.g., smartphones), optics (e.g., lasers), and biomedical devices (e.g., implants).

[0077] One strategy for creating reversible adhesives uses the thermally reversible Diels-Alder (DA) reaction as the crosslinking mechanism. The conventional DA reaction is a reliable and selective reaction between electron-rich dienes and electron-deficient dienophiles. This reaction is attractive for adhesives since mild temperatures (i.e., from room temperature to 80°C) can enable the formation of the DA adduct, while elevated temperatures (i.e., up to 150°C) can trigger dissociation, i.e., the retro-DA reaction. For example, studies by others have demonstrated a reversible epoxy-based adhesive enabled by a furan-maleimide DA reaction that cross-linked at 80°C and de-cross-linked at 150°C.

[0078] Beyond adhesives, the DA reaction has been used to make thermally reversible polymer networks for self-healing materials. Work by various groups include establishing the original self-healing furan-maleimide DA thermoset, applying this chemistry to silane-functional polymer hybrids, using a combination of furan-maleimide DA linkages and permanent covalent bonds formed via hydrosilylation to make a self-healing silicone for space applications, conducting a systematic evaluation of furan-functionalized PDMS, with furan functionalities ranging from 3-55%, cross-linked with various bismaleimides (e.g., aromatic vs aliphatic), and producing a room-temperature vulcanizing (RTV), self-healing silicone elastomer.

[0079] A comparatively underexplored dimension of furan-maleimide DA-based adhesives is the stereochemical outcome of cycloaddition, which may influence thermal reversibility and mechanical robustness. The kinetically favored endo adduct dissociates at lower temperatures (e.g., 50-120°C), whereas the thermodynamically favored exo adduct persists to higher temperatures (e.g., 110-140°C). Moreover, the endo adduct is more mechanically labile than the exo adduct. According to some embodiments of the present technology, the exo adduct may be improved or maximized, since it may permit use in solar photovoltaic applications, given its greater mechanical robustness and its higher dissociation temperature, which exceeds temperatures achieved under intense sunlight.International Patent Application Docket No. 009062.8583.WO00

[0080] PV materials, especially encapsulants, are designed for extended primary lifetimes and to withstand the conditions often used for low energy separations (water, operational temperatures, light, etc.). Embodiments of this technology overcome the false dichotomy between long primary lifetime and non-recyclability by advancing absorberagnostic reversibly cross-linking interlayer polymers (ReCLIP) to interface between existing encapsulants and solar cells (or simply “cell” for brevity). Such a reversibly-crosslinking polymer may have transformative effects on PV recycling if it meets the multifaceted thermomechanical demands on PV encapsulants or complement the properties of existing encapsulants by providing reversible adhesion. Switchable adhesion may enable ease of separation of PV module components at end of life. In some embodiments, heating the package at, e.g., 120-150°C may reverse cross-linking in the polymer interlayer and allow the cells to be “unzipped” from the package, providing access to the active material and valuable metals for recycling. Because forward crosslinking reactions in the ReCLIP occur at, e.g., 70°C, the interlayer may maintain mechanical stability during the operational lifetime of the PV package, with programmed delamination - unzipping - only when desired at end-of-life. Further, because of the reversible crosslink, the module may be “re-zipped” together to allow for refurbishing or repowering modules, according to some embodiments of the technology.

[0081] According to some embodiments, ReCLIPs may be used for “unzippable” solar cells. The technology leverages synthesis of polymers with targeted functional and mechanical properties and analysis of the defects and durability of PV cells and packages. The technology integrates one or more techniques including solvent-free methods to transfer conjugated polymer thin films for use in PV, multilayer graphene barrier layers for perovskite PV, thin film deposition methods that may affect conjugated polymer mechanical properties, and mechanically compliant conductive adhesives for PV. The technology builds off this collaboration in PV materials and devices to improve PV recyclability.

[0082] Aspects of the technology disclosed herein include: (1 ) reversibly cross-linking interlayer polymers (ReCLIPs) with chemical, optical, electrical, and mechanical properties tuned to interface favorably with commercial encapsulants and PV cells, (2) the recovery of Si PV cells from a ReCLIP package upon transient energy inputs afterInternational Patent Application Docket No. 009062.8583.WO00 accelerated aging of the package by exposure to damp heat and thermal cycling, and (3) minimum thicknesses of the ReCLIP required for successful “unzipping” of laminated packages to reduce material consumption.

[0083] Figure 1 A is a schematic illustrating the reversible “zip” and “unzip” functionality of a reversibly cross-linked interlayer polymer (ReCLIP) according to some embodiments of the present technology. In the upper portion of Figure 1A, a furan-functionalized polydimethylsiloxane (PDMS) (left) is combined with an aromatic bismaleimide crosslinker (center left) to form the cross-linked ReCLIP network (right) via a Diels-Alder cycloaddition reaction. In the “zip” direction (upper arrow), heating at a first temperature range (e.g., 50-80°C) drives the forward Diels-Alder reaction, forming thermally reversible crosslinks between the furan and maleimide moieties and resulting in a transparent, recyclable, adhesive polymer network disposed between two substrates (e.g., glass sheets). In the “unzip” direction (lower arrow), heating at a second, higher temperature range (e.g., 90-150°C) triggers the retro-Diels-Alder reaction, breaking the crosslinks and converting the adhesive network into a non-adhesive state, thereby allowing the substrates to be cleanly separated. The cyclic nature of the schematic illustrates that the zip and unzip process is repeatable, enabling multiple cycles of bonding and debonding.

[0084] The polymer (ReCLIP) disclosed in some embodiments of the present document constitutes a transformative enabler for, e.g., photovoltaic module recycling. According to some embodiments, ReCLIP is designed for compatibility with diverse PV technologies while working in tandem with industry-standard encapsulants like EVA, polyurethane, or POE. ReCLIP address recycling barriers by serving alongside existing encapsulants, facilitating efficient delamination and recovery of high-value materials, including PV cells (silicon) and substrates (e.g., glass), while relying on the existing mature encapsulant to ensure module robustness. Leveraging a low-energy stimulus responsive chemistry, ReCLIP enables clean separation outside the conditions of terrestrial operation, significantly reducing the energy and cost of recycling. This technology aligns with circular economy principles, addressing gaps in EoL handling and enabling the reuse and repowering of PV modules.International Patent Application Docket No. 009062.8583.WC00

[0085] Figure 1B is a schematic of ReCLIP in PV module integration, illustrating reversible cross-linking and potential insertion for facilitating delamination at end-of-life, according to some embodiments of the present technology. As shown in Figure 1 B, an intact PV module includes layers of glass, encapsulant, cell, encapsulant, and glass, with the reversibly cross-linking polymer positioned at one or more interfaces between the encapsulant and an adjacent layer. Upon application of a stimulus (e.g., heat), the crosslinked ReCLIP transitions to a de-crosslinked state, enabling the PV module components to be separated. This approach enables clean delamination of PV module components outside of terrestrial operating conditions, significantly reducing the energy and handling required to deliver high-purity material recovery. Unlike existing encapsulants, this polymer introduces a design that facilitates material separation while maintaining compatibility with existing PV manufacturing processes and absorber technologies.

[0086] In some embodiments, the at least one layer of the thermally reversible crosslinked polymer is disposed at one or more of: an interface between the first substrate and the encapsulant material, an interface between the second substrate and the encapsulant material, an interface between the encapsulant material and a photovoltaic cell, or any combination thereof. In some embodiments, two or more layers of the thermally reversible cross-linked polymer are disposed at two or more different interfaces within the photovoltaic module.

[0087] Some embodiments relate to a reversibly cross-linked interlayer polymer (“ReCLIP”) that cures by way of a thermally reversible Diels-Alder (DA) reaction between furan-functionalized silicone chains and an aromatic bismaleimide. Two-dimensional1H-1H correlation spectroscopy (COSY) nuclear magnetic resonance (NMR) experiments were used to distinguish between the exo and endo diastereomers of the furan-maleimide DA adduct. The exo-endo ratio exerted a pronounced influence on the thermal stability and adhesion strength of the resulting polymer network. With onedimensional1H NMR monitoring, we established that the Diels-Alder cross-linking proceeded most rapidly at approximately 80°C, while complete conversion and a high proportion of the exo adduct (approximately 93%) were also observed at approximately 60°C with extended reaction times. One-dimensional1H NMR also revealed that the onsetInternational Patent Application Docket No. 009062.8583.WO00 of the reverse (retro-Diels-Alder) reaction occurred at approximately 90°C. Using a lapshear geometry, ReCLIP exhibited a maximum shear strength of 286±50 kPa, comparable in magnitude to values seen for other silicone adhesives. Films exhibited desirable transparency and stability over time under ambient conditions.

[0088] Figure 2A is a schematic view of an “unzippable” PV package designed for circularity, according to some embodiments of the present technology. As shown in portion (A) of Figure 2A, an intact PV module includes a glass layer 210, a first encapsulant layer 220, a cell 230, a second encapsulant layer 240, and a glass / backsheet layer 250, with a reversibly cross-linked interlayer polymer (ReCLIP) 260 disposed at one or more interfaces between the encapsulant layers and adjacent layers. Portion (C) of Figure 2A provides a schematic view of the ReCLIP 260 in its adhesive elastomeric PDMS state, in which the PDMS chains are connected by Diels-Alder adducts formed between furan pendant groups and maleimide pendant groups, resulting in a cross-linked network. Upon application of heat greater than approximately 120°C, as indicated by the downward arrows between portions (A) and (B) and between portions (C) and (D) of Figure 2A, the Diels-Alder adducts dissociate via the retro-Diels-Alder reaction. Portion (B) of Figure 2A shows the separated PV module layers after de-crosslinking of the ReCLIP interlayer 260, enabling the glass 210, encapsulant 220, cell 230, encapsulant 240, and glass / backsheet 250 to be recovered. Portion (D) of Figure 2A provides a schematic view of the ReCLIP 260 in its non-adhesive oily PDMS state, showing the separated furan-functionalized PDMS chains and maleimide crosslinker species after dissociation.

[0089] As illustrated in Figure 2B, the interlayer 260 contains reversible cross-links based on the Diels-Alder reaction. The reversible Diels-Alder reaction may occur without catalyst or byproducts. As illustrated in Figure 2C, the Diels-Alder cross-links may be incorporated into PDMS via synthesis of two polydimethylsiloxane copolymers with complementary pendant groups 270 and 280 capable of cross-linking via the Diels-Alder reaction.

[0090] Figures 2A-2C illustrate a reversible Diels-Alder reaction that may be used to synthesize the “unzippable” interlayer for solar cell encapsulants. A significant advantage of this chemical approach is that the reversible Diels-Alder reaction occursInternational Patent Application Docket No. 009062.8583.WO00 without catalysts or byproducts but needs sufficient heat such that it does not occur under module operation. The combination of a silicone, polydimethylsiloxane (PDMS), and a Diels-Alder reaction may be used for a reversible adhesive interlayer for PV packaging.

[0091] Polydimethylsiloxane (PDMS) is a type of silicone rubber. Silicones are commonly used in electronics packaging and construction due to their chemical inertness, thermal stability, and optical transparency. However, PDMS exhibits poor adhesion to most substrates due to its low surface energy, high stiffness relative to pressure-sensitive adhesives, and lack of chemical functionalities to form covalent or van der Waals bonds with surfaces.

[0092] To address these and other challenges, PDMS may be functionalized with the furan and maleimide moieties needed for Diels-Alder cross-linking (Figures 3A-3C) and the reversible stiffening of the co-polymer (Figures 4A and 4B). The PDMS-Diels Alder reversible cross-linked polymers may be developed and evaluated in PV packages with an initial focus on, e.g., Si PV packages, which are widely used in the market. Close-knit design and evaluation cycles allow for tuning of ReCLIPs for PV.

[0093] In some embodiments, modules packaged with ReCLIP (e.g., single-cell minimodules packaged with ReCLIP) may be demonstrated to exhibit features including, (1) when pristine, having less than approximately 2% relative power conversion efficiency (PCE) loss with respect to a no-ReCLIP control, (2) passing DH1000 and TC50 with less than approximately 5% relative PCE loss with respect to controls, and (3) allowing delamination by thermal “unzipping” to extract the cell. To achieve these features, ReCLIPs may be characterized to determine their optical, electrical, and mechanical properties, as well as the energy needed for cross-linking and the retro-Diels-Alder “unzipping”. The polymer structure may be tuned to optimize these properties for PV application. The ReCLIP formulations may be applied to working PV devices and their performance evaluated before and after accelerated stress testing to demonstrate the reversible adhesion properties in PV packages. For instance, thousands of hours of accelerated testing of mini-module Si PV packages and root cause analysis of performance degradation may be performed. The full reversibility of the ReCLIP packaging may be demonstrated by unzipping and then re-zipping modulesInternational Patent Application Docket No. 009062.8583.WC00 (e.g., mini-modules) and evaluating their properties.

[0094] Embodiments of the technology may contribute to a diverse PV workforce and reduce the environmental burden that single-use PV waste places on communities. Embodiments of the technology development may substantially reduce the long-term constraints that PV currently places on communities by enabling circularity. Enabling PV module recycling may reduce the natural resource intensity of PV, decrease the burden of long-term cleanup costs, and potentially provide a pathway to more affordable second-life modules. Finally, re-zipping of modules, if successful, may allow the selective- and cost-minimized refurbishment and repowering of damaged modules, increasing climate resilience provided by PV.

[0095] Merely by way of example, PDMS copolymers containing pendant groups capable of Diels-Alder reaction may be synthesized as summarized in Figures 2A-2C. Complementary copolymers may be combined in solution, deposited as thin films, and cured at low temperatures (approximately 70°C) directly on solar cells to form a reversibly cross-linking interlayer polymer (ReCLIP). There may exist a temperature-dependence of the adhesion and mechanical properties of the polymer over the PV operating temperature range and up to approximately 150°C for disassembly. Laminates designed to isolate package interfaces for testing may be used to characterize mechanical strength, adhesion, and optical properties. Industry-standard accelerated aging tests including damp heat and thermal cycling may be performed on laminates of increasing stack complexity to isolate any impact of ReCLIP and provide feedback to tailor interface chemistry. Finally, optimized ReCLIP formulations may be applied to full PV packages and their performance evaluated before and after accelerated stress tests to de-risk that ReCLIP can be applied for reversible adhesion without substantial energy yield impacts.

[0096] Synthesized functionalized PDMS polymers may be used for validation of the reversible Diels-Alder cross-linking silicone co-polymer. Figures 3A-3C show the nuclear magnetic resonance (NMR) spectra of the functionalized PDMS polymers. The Diels-Alder reaction, e.g., the furan / maleimide adduct, may work as a reversible cross-linking agent. Initial cross-linking and de-linking experiments show the expected thermally reversible curing at approximately 70°C and flowing at approximately 135°C (Figures 4A and 4B). In some implementations, suspected impurities in the PDMS-maleimideInternational Patent Application Docket No. 009062.8583.WO00 precursor polymer may result in discoloration (e.g., a slight yellow color), which may be addressed through process optimization to meet optical transparency and other specifications for PV modules.

[0097] Figure 3A shows the1H NMR spectrum of PDMS-maleimide. Figure 3B shows the1H NMR spectrum of the starting material APTES-DMS. Figure 3C shows the1H NMR spectrum of synthesized PDMS-furan. The disappearance of the asterisk-marked signal in Figure 3B indicates that substantially all amine groups have reacted to form the maleimide moiety shown in Figure 3A or the furfuryl moiety shown in Figure 3C.

[0098] Figures 4A and 4B are photographic demonstrations of reversible cross-linking by Diels-Alder reaction of the functionalized PDMS, according to some embodiments of the present technology. As shown in Figure 4A, the material cured at approximately 70°C reaches a gel point and exhibits solid-like behavior. As shown in Figure 4B, upon heating to approximately 135°C, the material de-crosslinks and flows easily, confirming the thermal reversibility of the Diels-Alder crosslinks.

[0099] The reversible cross-linking polymer technology may cleanly separate laminate subcomponents to improve circularity. Current commercial techniques to separate solar cells from their packaging involve high temperature pyrolysis and / or mechanical techniques to break down cross-linked EVA, POE, or polyurethane encapsulants and separate the module into raw materials. Intractability of the polymer encapsulants makes it difficult to extract the solar cells and valuable metals. The cost to process EOL modules for reuse or material extraction may exceed the potential revenue using conventional approaches.

[0100] A ReCLIP-based recycling process may reduce the cost for reuse or material extraction as it may need only mild heating to separate the cell from front and back sides. Such a process may remove the need for high-temperature pyrolysis furnaces and preprocessing to remove toxic fluoropolymer backsheets, or may avoid mechanical glass cutting and large-scale sieving. If these large capital costs are removed from the technoeconomic model of existing recycling processes and the capital and labor for a relevant 100-140°C treatment (e.g., as included in existing models for backsheet peeling) are retained, ReCLIP-based delamination may reduce recycling costs by approximately $350 / ton, or a reduction of about 30% of recycling costs, according to some estimates.International Patent Application Docket No. 009062.8583.WO00 The reversible polymer can be applicable to modules of any absorber and applies even if the module or cells have been fractured.

[0101] In addition to cost and energy reduction, ReCLIP processes may provide value-added recovery of low mass fraction Ag and Si in Si PV modules and a direct path to reclaiming the hazardous elements of CdTe and perovskite absorbers by directly exposing them forextraction.

[0102] By way of example, recovering the glass, Al, and Cu from a 60-cell Si module may offer approximately $3 / module. Separating the Si cell cleanly from the encapsulant and glass using a ReCLIP may open up additional revenue streams. Extracting Si from each 60-cell module can bring an additional $3 for second-grade Si or up to approximately $4.24 for solar grade silicon, increasing revenue from recycling by up to approximately 100%. Prior analysis by others suggests that similar high-value recycling scenarios promise net revenues of approximately $0.01-0.02 / W from project decommissioning. Because of the ease of extracting the high value absorber, metals, and transparent conductive oxides (TCOs) from PV technologies, ReCLIPs may make a significant step toward reducing net recycling costs by half and achieving lower levelized cost of energy (LCOE), e.g., $0.02 / kWh.

[0103] Developing a material that adheres reversibly to the front and back side of the cell and commercial encapsulants (EVA, polyolefin elastomers (POE)) and does not affect the lifetime energy yield is a challenging task. Encapsulation must meet multi-fold optical, electronic, mechanical, adhesive, chemical, thermal, and economic requirements to succeed in PV. On the other hand, silicones have already been successfully commercialized for use in fielded PV modules because of their many advantageous physical and chemical properties. Among them:

[0104] PDMS has stable transparency deeper into the UV than EVA, POE, or polyurethane. Its refractive index is favorable for the cell interface at approximately 1.4 and tunable by side groups. PDMS has been used as a beneficial scattering layer in high-efficiency perovskite on silicon tandem solar cells.

[0105] PDMS does not swell in the presence of moisture and holds an order of magnitude (OoM) lower equilibrium moisture content relative to EVA. When used as an interlayer, a reduced interfacial moisture concentration by an order of magnitude may beInternational Patent Application Docket No. 009062.8583.WO00 achieved, which may increase robustness against corrosion and delamination relative to EVA.

[0106] PDMS is an insulator with bulk resistivity roughly 1.5 orders of magnitude higher than EVA, which may add potential-induced degradation (PID) resistance when used as an interlayer. PDMS is compatible with use in even highly concentrated (e.g., 17M) acetic acid environments, such that the acidic environment that can develop within EVA-encapsulated packages upon moisture exposure should have no meaningful effect.

[0107] The silicone ReCLIP may also be favorable relative to EVA for adhesion to oxide / dielectric interfaces. Unlike EVA, where only a small fraction of silane adhesion promoters can be present, the PDMS can chemically adhere with high bond density. The adhesion promoters in the EVA that help bonding to, e.g., glass may undergo similar condensation reactions and irreversibly bond to the silicone, serving a similar function and likely providing high toughness at the EVA / interlayer interface without needing modification to EVA formulations.

[0108] PDMS has an elastic modulus at least one order of magnitude lower than EVA, with a glass transition temperature below the range of PV operation (e.g., approximately -50°C). The interlayer may provide additional compliance to relieve residual stresses at the cell level that can lead to failure.

[0109] Others have investigated a related “double encapsulation” approach, wherein non-adhesive polymer layers were introduced over cells within standard EVA-encapsulated packages. Although cell recovery was achieved, the concept was ultimately unviable since the cells and strings floated within the non-adhesive layers. Poor optical coupling also arises at a non-adhesive polymer / cell interface due to airgaps, which others addressed by applying a silicone interlayer to improve short-circuit current density (Jsc) to within approximately 1.5% relative of the control. The silicone ReCLIP approach according to some embodiments of the present technology disclosed herein has several advantages with respect to these prior efforts. The ReCLIP may allow unzipping at temperature, while providing adhesion and mechanical integrity during field operation and optical coupling. Patterning or positioning of the silicone with respect to the cells during layup may be omitted.International Patent Application Docket No. 009062.8583.WO00

[0110] Embodiments of the technology may address one or more of the following: (a) ensuring sufficient cross-linking occurs at the interfaces of the ReCLIP to promote adhesion between cell and encapsulants (e.g., commercial encapsulants such as EVA), (b) optimizing a process for application of the adhesion layer, and (c) avoiding property and performance changes over time during environmental exposure. Exemplary approaches for addressing each of these are described below.

[0111] To improve cross-linking density and adhesion to commercial encapsulants, the number of Diels-Alder adducts may be increased, thereby introducing small molecule cross-linkers to improve adhesion, or silane adhesion promoters like those used in EVA, if needed.

[0112] To optimize the application of the ReCLIP, blade coating or spraying may be performed to create thin layers (e.g., 1-10 micrometers) of neat ReCLIP. To ensure uniform layers, the substrates may be heated to promote retro Diels-Alder or uncrosslinking and then cooled back down to cross-link the ReCLIP. This process is compatible with methods used in industry.

[0113] To maintain energy yield over time, alternative Diels-Alder adducts as well as small molecule cross-linkers, may be used, which can provide a wider range of mechanical and kinetic properties. If parasitic absorptions arise over time, non-aromatic Diels-Alder adducts may be used. The ability to “unzip” may be improved by tailoring the material to provide improved performance in adhesion and solar cell efficiency. These approaches, alone or in combination, may allow the development of, at minimum, an absorber agnostic adhesion layer for PV units that may facilitate removal of the solar cell.

[0114] The reversible cross-linking polymers as disclosed herein may facilitate low-temperature separation of the glass and encapsulants from PV cells. The technical features may include one or more of the following. A first technical feature includes a reversible polymer adhesion interlayer to allow for “unzipping” of end-of-life PV modules at low temperatures. Polysiloxanes functionalized with Diels-Alder adducts, e.g., the furan / maleimide adduct, allow for adhesion promoting cross-linking at, e.g., approximately 70°C. The cross-linked polymer network may be stable and adhesive at PV operating and test temperatures (e.g., lower than approximately 85°C), given that forward cross-linking reactions occur at, e.g., approximately 70°C. The cross-linking can be reversed via retro-International Patent Application Docket No. 009062.8583.WO00 Diels-Alder at relatively low temperatures, e.g., approximately 120-150°C, effectively reversing the adhesion between the solar cell and encapsulant only outside PV operating conditions. These forward- and reverse-cross-linking temperatures can be manipulated by selected moieties. Clean separation of the solar cell and glass may be enabling for reuse or recycling of the separate components. Because the cross-linking reaction is reversible, theoretically ReCLIP can allow for modules to be “rezipped” and reused if desired.

[0115] A second technical feature includes synergistic mechanical, thermal, and chemical compatibility with current processing and lamination techniques using commercial encapsulants (e.g., EVA, POE), serving as a potentially “drop-in” technology to enable circularity. The ReCLIP approach leverages the development of commercial encapsulants (e.g., EVA, POE), lamination processes, and cell architectures. For example, by using existing backside encapsulants for bifacial modules with UV-blocking characteristics, the ReCLIP need not be UV blocking. If hot spots raise temperature locally to above the de-linking temperature, the EVA, POE, or polyurethane encapsulant may serve to maintain integrity until the temperature cools and the ReCLIP re-crosslinks. The ReCLIP may be not only compatible but synergistic with existing encapsulants.

[0116] Keeping the EVA / POE encapsulant may offer a cost benefit, because bulk silicones have historically proven too costly for replacing EVA / POE in utility PV. Instead, an interfacial layer may be used, and the thickness of the ReCLIP can be reduced or minimized while maintaining ease of separation. It is possible that the ReCLIP need be only a small fraction of the total polymer, reducing added costs, which may in turn be offset by possible durability gains. Because silicones are well-known for desired transparency and durability in PV packages, including the ReCLIP may not reduce but rather improve performance and durability.

[0117] A third technical feature includes the selection of adhesion layer chemistry for its absorber agnosticism, chemically and / or optically, to enable substantially lossless introduction across PV products. The high yield, selectivity, and mild reaction conditions of Diels-Alder reactions may lead them to be classified as “click-like,” because of their similarities to “click” chemistry. The DA adduct formation as disclosed herein may yield substantially no reactive byproducts and does not require a catalyst to proceed.International Patent Application Docket No. 009062.8583.WO00

[0118] The development of the absorber-agnostic ReCLIP may facilitate materials separation to improve end-of-life handling across PV and enable energy- and costefficient recovery of component materials at end-of-life. The technology may change the trajectory of the materials balance in the PV industry away from single use towards PV technologies that could last for generations of re-use.

[0119] Because of its reversibility, the ReCLIP offers not only a path to facile recovery of valuable cell components, it may also offer the opportunity to actively repair or replace cells in strings or tandem architectures. Notably, one of the challenges of emerging PV technologies is ensuring their durability to achieve bankability without decades-long demonstrations. By enabling module refurbishment, ReCLIPs may streamline the fielding of higher-efficiency PV by mitigating downside risk.

[0120] According to some embodiments, the technology as disclosed herein may include one or more of the following aspects:

[0121] - Developing reversibly cross-linking interlayer polymers (ReCLIPs) with chemical, optical, electrical, and mechanical properties tuned to interface favorably between commercial encapsulants and cells.

[0122] - Demonstrating the recovery of Si PV cells from a ReCLIP package after transient heating below, e.g., approximately 200°C after accelerated aging of the package by exposure to damp heat and thermal cycling.

[0123] - Identifying minimum thicknesses of the ReCLIP required for successful “unzipping” and “re-zipping” of laminated packages to reduce material requirements.

[0124] Implementations of some embodiments of the technology are described herein in one or more of three phases. Each contains two stages: one stage focused on synthesis and manipulation of polymer properties that runs ahead of a second stage focused on validating integration and durability of the ReCLIPs in packages. A first phase includes synthesizing and characterizing the properties of the baseline ReCLIP on mg to multi-gram scales. The increased quantities may be used to investigate the compatibility of interfaces of the ReCLIP with encapsulant and package materials. A second phase includes demonstrating successful unzipping of PV modules (e.g., Si mini-modules) using ReCLIPs. Integration and testing of modules (e.g., Si mini-modules) may be supported by the manipulation of the mechanical, adhesive, and cross-linking properties of theInternational Patent Application Docket No. 009062.8583.WO00 ReCLIP to enable co-optimization to the needs of PV packages. A third phase includes evaluating durability of unzippable Si PV packages, demonstration in packages containing other absorbers where refurbishing may be particularly helpful (e.g. perovskites), and minimizing the quantity of ReCLIP required to enable facile delamination. Where feasible, materials and equipment used may be domestically sourced.

[0125] In some embodiments, synthesis and characterization of reversibly-crosslinking polymers may include characterizing the temperature-dependent properties of a baseline reversible cross-linking co-polymer and scaling the synthesis to multi-gram scales to enable testing in, e.g., mini-modules.

[0126] Synthesizing functionalized PDMS for cross-linking may include synthesis of precursors to the ReCLIP. In some embodiments, the precursors include a PDMS functionalized with a first Diels-Alder reactive group (e.g., furan-functionalized PDMS (PDMS-furan)) and a crosslinker including a second, complementary Diels-Alder reactive group (e.g., a small molecule bismaleimide or a maleimide-functionalized PDMS (PDMS-maleimide)). The amine functional groups on the amine-functionalized PDMS precursor may be (substantially) completely converted to the target pendant groups (e.g., furan or maleimide moieties). The conversion may be analyzed by one or more of: (1)1H NMR and Fourier-Transform Infrared spectroscopy (FTIR) to determine the fraction of the polymer functionalized by the target pendant groups, or (2) thermogravimetric analysis (TGA) to examine the thermal range of stability of the functionalized polymer. Repeatable polymer synthesis may be demonstrated.

[0127] In some embodiments, the first Diels-Alder reactive moiety on the pendant group comprises a diene moiety and the crosslinker comprises two or more dienophile moieties. In some embodiments, the first Diels-Alder reactive moiety on the pendant group comprises a dienophile moiety and the crosslinker comprises two or more diene moieties. For example, maleimide moieties may be incorporated as pendant groups on the polysiloxane backbone, and a bis-furan or multi-furan compound may serve as the crosslinker. The choice of which reactive moiety resides on the backbone versus the crosslinker may be selected based on synthetic accessibility, desired crosslink density, and target mechanical properties. In each configuration, the Diels-Alder cycloadditionInternational Patent Application Docket No. 009062.8583.WO00 proceeds between the complementary diene and dienophile to form thermally reversible crosslinks.

[0128] Cross-linking and de-linking of the co-polymer and reaction characterization may include establishing conditions (temperature, time, solvent) needed to cross-link PDMS-furan and PDMS-maleimide to form the ReCLIP. The ReCLIP may be cross-linked and de-crosslinked by heating and the reaction characterized as a function of temperature by, e.g.,1H NMR, FTIR, and Raman spectroscopy to determine fraction cross-linked and product purity, differential scanning calorimetry (DSC) to quantify the energy required to cross-link, dynamic mechanical thermal analysis and tensile testing to examine mechanical properties, TGA to determine decomposition temperature, and ultraviolet-visible spectroscopy (UV-Vis spectroscopy or UV-Vis). The Arrhenius behavior or kinetics of the cross-linking and de-crosslinking reaction may be investigated by, e.g., monitoring the concentration of maleimide groups via UV-Vis at 310 nm, tracking signature furan and maleimide peaks in NMR, or using Raman spectroscopy and comparing intensity of furan, maleimide, and the furan / maleimide adduct peaks. An understanding of the kinetics and temperature dependence may help iterate future formulations.

[0129] Scaling the ReCLIP synthesis to, e.g., gram scales or higher, may include establishing conditions for larger scale (e.g., greater than 10 grams) synthesis of PDMS-furan and PDMS-maleimide to provide product co-polymer for introduction and testing in PV packages. Each batch may provide greater than approximately 750 cm2of functional ReCLIP assuming a characteristic test thickness of approximately 100-micrometer layers. Scaling to the multigram scale may involve efficient mixing techniques. Because the ReCLIP reactions are not very oxygen sensitive, standard equipment such as a glovebox and overhead stirrer may be used.

[0130] In some exemplary implementations, batches of functionalized polymer may be produced for a total of greater than approximately 5 grams with greater than approximately 90% amine groups replaced with furan or maleimide functional groups.

[0131] In some exemplary implementations, co-polymer may be demonstrated with greater than approximately 60% of the reversible cross-links linked at lower than approximately 80°C and de-crosslinking demonstrated at higher than approximately 100°C, verified spectroscopically and mechanically.International Patent Application Docket No. 009062.8583.WO00

[0132] In some exemplary implementations, greater than approximately 10 grams of ReCLIP may be produced at greater than approximately 80% yield with higher than approximately 90% conversion of amine groups. In some implementations, batch-to-batch consistency may be demonstrated by achieving three or more batches of ReCLIP at greater than approximately 10-gram scale with cross-linked fraction within approximately 15% absolute variation and de-linking temperature higher than 100°C and within 10°C variation.

[0133] According to some embodiments, testing the interfaces of cross-linking polymers with common package materials may include characterizing the compatibility of the ReCLIP with an encapsulant (e.g., EVA, POE, or polyurethane encapsulants) as a function of damp heat and thermal cycling. Systematic interface-by-interface analysis may identify one or more weak links and opportunities for polymer design to address them.

[0134] In some exemplary implementations, integration of ReCLIPs in laminates may include fabricating standalone ReCLIP layers and small-area (e.g., approximately 1x1 inch) glass-glass and glass-backsheet packages with ReCLIP, EVA / ReCLIP / EVA, and POE / ReCLIP / POE laminates. In some implementations, encapsulants and / or backsheets may be sourced commercially, e.g., from Dow, other members of the Duramat consortium. Methods for deposition of the ReCLIP such as liquid casting into molds, spin-coating, blade-coating, and spray-coating may be applied to vary one or more parameters including, e.g., thickness, coverage, and / or polymer microstructure. Lamination timetemperature profiles may be optimized to integrate the ReCLIP, e.g., based on supplier recipes.

[0135] In some exemplary implementations, characterization of pristine ReCLIP-encapsulant laminates may include bulk conductivity tests as a function of cross-linking / temperature on the standalone ReCLIP layers with appropriate guard electrodes and a high-voltage sourcemeter. In some exemplary implementations, glass / ReCLIP / glass laminates may be used in a baseline lap shear test as a function of temperature to determine baseline shear strength versus temperature and cross-linking reversibility. In some exemplary implementations, optical properties may be compared across laminates by UV-Vis spectroscopy. In some exemplary implementations, 180° peel testing may be used to examine adhesion after inserting a separator (e.g., a TeflonInternational Patent Application Docket No. 009062.8583.WO00 separator) at the edge during lamination to select the interface to start the peel of a long tab on the backsheet, following protocols developed previously on encapsulant durability. See, e.g., N.C. Theut et al., Conf. Rec. IEEE Photovolt. Spec. Conf. 2020-June, 2057 (2020), which is incorporated by reference. Interface analysis following failure by, e.g., microscopy, profilometry, FTIR, and X-ray photoelectron spectroscopy (XPS), may examine the fraction of cohesive failure.

[0136] In some exemplary implementations, characterization of damp heat (DH) and thermal cycling (TC) exposed ReCLIP-encapsulant laminates may include DH500, dry thermal exposure at approximately 85°C (relative humidity (RH) less than approximately 10%), and TC25 exposures to preliminarily screen the compatibility of the encapsulant-ReCLIP laminates. In some exemplary implementations, lap shear and peel testing as a function of temperature may determine aged shear strength and adhesion versus the baseline, as described elsewhere in the present document. FTIR, Raman spectroscopy, DSC, and Soxhlet extractions may be used as needed to examine a suspected change in cross-linked fraction over time. For example, the DSC peak area for the cross-linking exothermic Diels-Alder reaction and the endothermic reverse reaction is expected to change based on fraction cross-linked.

[0137] In some embodiments, pristine toughness of t he weakest interface in a glass-EVA-backsheet laminate with ReCLIP may be greater than approximately 85% of a no-ReCLIP control.

[0138] In some embodiments, aged toughness of the weakest interface in a glass-EVA-backsheet laminate with ReCLIP may be greater than approximately 85% of a no-ReCLIP control.

[0139] According to some embodiments, tuning ReCLIP properties to design for diverse, durable integration may include advancing strategies to tailor the temperature-dependent properties of the ReCLIP to optimize for application in PV, including Si and thin film packages.

[0140] The mechanical stiffness of the co-polymer may be tuned by one or more of the following strategies: (1) varying the number of cross-linkable groups along the PDMS chain, (2) introducing small molecule cross-linking agents such as 1 ,1 ’-(methylenedi-4,1 -phenylene)bismaleimide or bis-maleimidoethane (Figure 5A), and / or (3) introducingInternational Patent Application Docket No. 009062.8583.WO00 irreversible cross-links via hydrosilylation (Figure 5B). In strategy (2), the small molecule bismaleimides may eliminate the need for PDMS-maleimide, reducing the uncross-linked PDMS content and increasing stiffness. Strategy (3) may be implemented if a significant increase in mechanical stiffness is required. Si-H and Si-vinyl groups may be introduced in the PDMS chains to include a fraction of irreversible cross-linking (Figure 5B). Tensile and lap shear testing may be performed on modified formulations to quantify and correlate changes in mechanical stiffness to modifications in polymer structure. Techniques including FTIR, Raman spectroscopy, and DSC, may be used to correlate degree of cross-linking to changes in mechanical stiffness.

[0141] Figure 5A shows exemplary bismaleimide cross-linking agents, and Figure 5B shows exemplary irreversible cross-links using vinyl-hydride groups for hydrosilylation. Stiffness of the ReCLIP may be increased by including bismaleimide cross-linking agents (Figure 5A) and / or irreversible cross-links via hydrosilylation (Figure 5B).

[0142] Modulating the interfacial adhesion may include introducing reactive end or side groups to the polysiloxane backbone. EVA formulations include silane adhesion promoters - silane small molecules with reactive moieties. This strategy may be beneficial since the ReCLIP may have a polysiloxane backbone. Synthesizing polysiloxane with small fractions of reactive end or side groups (e.g., methacrylates, methoxy groups, hydroxyl groups) may promote adhesion between the ReCLIP and a solar cell or EVA. Changes in interfacial adhesion may be quantified via lap shear testing and 180° peel testing. Figure 6 shows examples of reactive end or side groups (R) that can react with EVA or the Si cell to improve interfacial adhesion.

[0143] Establishing levers to control cross-linking and de-linking temperature may include developing alternative Diels-Alder (DA) couples that react at a lower temperature (e.g., cyclopentadiene) and a higher temperature (e.g., pyrrole / cyclohexene) than the furan / maleimide couple to expand the thermal range for cross- and de-linking. Figure 7 shows that the cyclopentadiene DA couple (a) and the pyrrole / cyclohexene couple (b) offer opportunities for cross-linking at different temperatures. As shown in portion (a) of Figure 7, the cyclopentadiene-based DA couple may cross-link at a lower temperature relative to the furan / maleimide couple. As shown in portion (b) of Figure 7, the pyrrole / cyclohexene DA couple may provide a higher cross-linking temperature (e.g.,International Patent Application Docket No. 009062.8583.WO00 forward reaction at about 90°C) and a higher de-linking temperature (e.g., reverse reaction at about 110°C).

[0144] In addition, other dynamic covalent bonds may be employed, including disulfide bonds, dioxaborolane metathesis, and vinylogous urethane exchange. These reversible reactions all occur in varying temperature ranges. All may proceed without catalyst or byproducts. Characterization of the new polymers may follow that used for the baseline ReCLIP.

[0145] Diels-Alder cycloaddition is described herein as an exemplary reversible crosslinking chemistry and not intended to be limiting. Other reversible covalent bonding chemistries may be employed to form the reversible crosslinks. In some embodiments, the reversible covalent crosslinks comprise disulfide bonds, which may be formed between thiol-functionalized pendant groups on the polysiloxane backbone and a crosslinker comprising two or more thiol groups, and which may be broken by reduction or thiol— disulfide exchange. In some embodiments, the reversible covalent crosslinks comprise dioxaborolane linkages formed between diol-functionalized pendant groups and boronic ester crosslinkers, which may undergo metathesis exchange under appropriate conditions. In some embodiments, the reversible covalent crosslinks comprise vinylogous urethane linkages, which may undergo exchange via transamination. Each of these alternative chemistries may provide different activation temperatures, exchange kinetics, and mechanical properties, enabling the reversible crosslinked polymer to be tailored for specific application requirements. Combinations of two or more reversible crosslinking chemistries within the same polymer network are also contemplated.

[0146] In some embodiments, tuning of ReCLIP properties may include synthesis of alternative cross-linking agents to tailor material properties and / or increasing a limiting property (e.g., a most limiting property) of baseline ReCLIP by, e.g., greater than approximately 25% relative in an optimized ReCLIP (e.g., de-linking temperature, adhesion, or stiffness).

[0147] According to some embodiments, “unzipping” modules (e.g., Si mini-modules) may include developing modules that can be easily delaminated by incorporating the ReCLIP interlayer. In some implementations, demonstrations may be on freshly-assembled modules (e.g., mini-modules), with subsequent demonstration of unzippingInternational Patent Application Docket No. 009062.8583.WO00 using damp heat and dry heat exposed modules (e.g., mini-modules) to provide indication of likely viability of the procedure at module end-of-life.

[0148] In some implementations, ReCLIP-integrated modules (e.g., ReCLIP-integrated small area Si mini-modules) may be assembled with differing coverages to assess or isolate effects of the interlayer. For example, active-area (e.g., 2x2”) glass-backsheet Si mini-modules with and without the ReCLIP may be assembled to assess or isolate effects of the interlayer. In some implementations, EVA may be used as the encapsulant, as it holds a dominant market share. It may be feasible to unzip while non-conformally covering metallization and tabs with ReCLIP. Metal-encapsulant interfaces may offer poor adhesion in PV packages, and fingers, busbars, and tabs may have significant relief relative to the cell surface (e.g., physically protruding from the cell surface, creating a non-planar, uneven topography). ReCLIP may be applied onto a cell by, e.g., liquid casting, spraying, or the like, or a combination thereof. In some implementations, partial or complete coverage of this topography may provide successful cell recovery.

[0149] To facilitate characterization and / or delamination of pristine ReCLIP-integrated modules (e.g., Si mini-modules), current-voltage (IV) curves of pristine packages may be employed to identify initial performance losses and / or benefits from incorporating the ReCLIP versus EVA-only controls. Lap shear testing as a function of temperature may determine baseline shear strength and be used to demonstrate the “unzipping” of Si packages. Post-delamination interface analysis (e.g., microscopy, profilometry, FTIR, XPS) may examine the failure mode and the chemistry of the interfaces. Additional characterization such as UV-Vis and photoluminescence / electroluminescence (PL / EL) imaging may be used to determine causes of any losses or gains with respect to controls.

[0150] Temperature-programmed delamination of aged ReCLIP integrated modules (e.g., ReCLIP-Si mini-modules) may be performed using DH500, dry thermal exposure at approximately 85°C (RH less than approximately 10%), and TC25 exposures to probe the chemical and mechanical compatibility in the ReCLIP-cell laminates. Similar characterization may be carried out as for the pristine packages to analyze the root causes of any increased or slowed degradation with respect to ReCLIP-free controls. Aging results may be fed back for iterative design, e.g., to improve adhesion or stiffness.International Patent Application Docket No. 009062.8583.WO00

[0151] In some implementations, ReCLIP adhesion to cell interfaces may be investigated by 180° peel testing with the ReCLIP at Si cell interfaces, both pristine and after, e.g., DH, dry heat, and TC25 exposures. For instance, adhesion to unmetallized passivated emitter and rear contact (PERC) (dielectric interface) and heterojunction technology (HJT) (TCO interface), metallized PERC and HJT (front and back, mixed metal and dielectric / TCO interfaces) may be analyzed to indicate whether the silicone changes adhesion to the metal versus the poorly adhesive state of the art. The uncoated surface of the cell may be glued to a piece of glass for testing, and backsheet strips attached to the ReCLIP to provide tabs for peeling, following previous protocols in, e.g., N.C. Theut et al., Conf. Rec. IEEE Photovolt. Spec. Conf. 2020-June, 2057 (2020), which is incorporated by reference.

[0152] In some embodiments, PV modules (e.g., Si PV mini-modules) containing the ReCLIP may be cross-linked and uncross-linked for pristine packages.

[0153] For instance, packages of Si PV coupons (e.g., approximately 2x2 inch) may exhibit no creep after DH500, while still unzipping thereafter at greater than approximately 100°C.

[0154] According to some embodiments, the interlayer may be refined for manufacturability and / or cost. For instance, the limits of reversibility may be shown as a function of ReCLIP thickness and area size to guide manufacturing and integration process bounds.

[0155] In some embodiments, mechanical properties may be evaluated as a function of ReCLIP thickness by thin film deposition including blade coating and spin coating to produce polymers of varying thickness from bulk layers (approximately 100 micrometers) down to single- to sub-micron thicknesses. These films may be bonded in glass-glass laminates and tested in lap shear to examine the limits of the mechanical reversibility of the ReCLIP at small thicknesses.

[0156] In some implementations, ReCLIP deposition may be scaled to test reversible lamination of cells of different sizes (e.g., M6-sized cells). Several 10-gram (or larger) batches of polymer may be synthesized. Process variation may be analyzed across the ReCLIP batches. Deposition may be scaled to cover cell areas of interest (e.g., M6 sized areas). Quarter cell, half cell, and full cell areas may be tested in temperature-International Patent Application Docket No. 009062.8583.WO00 dependent lap shear to confirm that properties are maintained with scaling.

[0157] In some implementations, thickness-dependent ReCLIP mechanical properties over at least approximately 1-100 micrometers may be assessed. In some implementations, delamination force may scale with areal size up to, e.g., M6 or similar or equivalent cell sizes, enabling projection of full module behavior.

[0158] In some implementations, de-risking ReCLIP integration on performance and / or durability may include tracking the performance of ReCLIP-packaged single-cell modules (e.g., M6 single-cell Si mini-modules) during accelerated aging tests and demonstrating “unzipping” afterward. ReCLIPs may be applied to other absorbers, including perovskites as perhaps the most chemically sensitive. Re-lamination of ReCLIP packages may be performed, demonstrating the potential for use in refurbishment or repowering.

[0159] In some implementations, ReCLIPs may be applied to encapsulate alternative absorbers. For instance, ReCLIP packages may be laminated using non-Si absorbers, e.g., perovskite solar cells (e.g., 1 ” substrate perovskite solar cells), CdTe cells, or cells from other sources, to demonstrate absorber agnosticism.

[0160] In some implementations, damp heat and thermal cycling studies with 8” ReCLIP packages may include extending small-area tests to demonstrate performance, durability, and “unzipping” in single-cell mini-modules with larger cell sizes (e.g., M6). PL / EL imaging of series resistance and local diode characteristics may be leveraged to clarify any degradation or improvements relative to no-ReCLIP controls.

[0161] In some implementations, Si packages may be re-laminated for circularity, facilitated by the reversibility of the cross-linking over multiple cycles of lamination and “unzipping.” The PCE of the module and cell may be monitored after lamination and delamination, respectively, to elucidate any process interactions. For instance, coupon packages (e.g., approximately 2x2 inch) may be used for 180° peel testing to probe adhesion in successive cycles of lamination and delamination.

[0162] In some implementations, de-risking integration may include: demonstrating that a non-silicon solar cell package may be “unzipped,” demonstrating unzipping and re-zipping of a pristine single-cell (e.g., M6 cell) mini-module with lower than approximately 5% PCE loss relative to initial laminated value.International Patent Application Docket No. 009062.8583.WO00

[0163] For example, an M6-sized (166 mm x 166 mm) single-cell mini-module that incorporates a ReCLIP interlayer may show less than 2% relative power conversion efficiency (PCE) loss when pristine (i.e., before any aging) compared to an identical control module without ReCLIP with statistical significance.

[0164] As another example, M6-sized single-cell mini-modules packaged with ReCLIP may pass two standard accelerated aging tests — DH1000 (damp heat at 85°C / 85% RH for 1000 hours) and TC50 (50 thermal cycles) — with less than 5% average relative PCE loss compared to no-ReCLIP controls. Additionally, after aging, the modules may still demonstrate temperature-programmed delamination (i.e., the ReCLIP may successfully "unzip").

[0165] An authoritative assessment of PV recycling indicates the cumulative technical potential of recoverable materials in EOL modules by 2050 may be valued at approximately $15 billion. Embodiments of the technology may target a largest share of this market for nearest-term introduction of ReCLIPs by focusing on Si PERC in its performance and durability demonstrations. The durability of ReCLIPs may be systematically de-risked at dielectric, metal, encapsulant, and TCO interfaces, with a focus on, e.g., accessing the full PV market (e.g., TOPCon, CdTe, HJT, perovskite, tandem, and other architectures).

[0166] The ReCLIP approach and the applicability of the technology for PV may have an impact on silicone and polyolefin elastomer manufacturing.

[0167] The development of the technology may involve the synthesis of polymers with designer properties. Figures 8A-8D illustrate synthesis and characterization of mechanically compliant conductive polymers. Figure 8A illustrates the synthesis of PEDOT:PSS-b-PPEGMEA. Figure 8B shows stress-strain curves. Figure 8C shows resistance-strain curves. Figure 8D shows strain at failure and toughness for different formulations. By using a block copolymer of PSS with a “soft” poly(poly(ethyleneglycol) methyletheracrylate) block, the produced conductive elastomers may have improved toughness (e.g., 10 times improvement) and higher strain (e.g., 2-10 times higher strain) at failure compared to commercial formulations (PSS-block-PPEGMEA). The development of the technology may also involve conducting statistically meaningful durability studies of PV packages with root cause analysis using advancedInternational Patent Application Docket No. 009062.8583.WO00 spectroscopic characterization and PL-IV imaging. For example, Figures 9A-9D illustrate results obtained using 2500-or-more-hour tests to discriminate between moisture-induced effects in glass-glass versus glass-backsheet Si packages. Multilevel humidity and thermal testing over thousands of hours may parse out effects of environmental stressors that depend on module architecture, using PL-IV imaging and correlative water reflectometry.

[0168] Figure 9A illustrates an experimental matrix showing multi-level humidity (0-85% relative humidity) and thermal (25-85°C) testing conditions applied over a period of 0 to 2500 hours. Figure 9B shows two module architectures tested: glass-glass and glass-backsheet configurations, each comprising glass, EVA encapsulant, cell, EVA encapsulant, and glass or backsheet layers. Figure 9C illustrates the characterization approach, including photoluminescence current-voltage (PLIV) imaging to extract series resistance (Rs) and finger interrupts, and water reflectometry and dosimetry (WaRD) to monitor water content and dose. Figure 9D shows normalized PCE (PCE / PCE0) as a function of time for glass-glass and glass-backsheet modules at 65°C and 85°C under 0%, 40%, and 85% RH conditions, with deconvolution of causes leading to PCE losses including interrupts, background series resistance, and net effects.II. Example Performance Parameters and Benchmarking

[0169] The adhesion strength between different interfaces in a photovoltaic module is documented in scientific literature. This data helps ensure adherence to industry and academic standards for adhesion strengths across the interfaces of interest. Sufficient adhesion between the module layers is desirable for maintaining the durability, mechanical integrity, electrical performance, prevention of moisture ingress, and safety of PV modules. Merely by way of example, there are at least three distinct interfaces within a photovoltaic module involving the polymer encapsulant(s): (1) encapsulant / glass, (2) encapsulant / cell, and (3) encapsulant / backsheet.

[0170] Figure 10 shows the range of adhesion strengths at EVA interfaces reported in scientific literature. From the data, the adhesion strengths at each interface are approximately: 10 ± 2 N / mm for encapsulant / glass, 3.5 ± 1 N / mm for encapsulant / cell, and 5 ± 2 N / mm for encapsulant / backsheet. These values may serve as benchmarks for evaluating the performance of ReCLIP-enhanced laminates.International Patent Application Docket No. 009062.8583.WO00

[0171] Hot spot temperature measurements may reveal a range of temperatures that may be considered for the long-term stability and functioning of cross-linking polymers. Literature findings suggest temperature ranges starting from around 21 °C to elevated temperatures as high as 150°C.

[0172] A number of reports identified hot spot temperatures exceeding 120°C, primarily in older cell and module architectures dating back more than 10 years. These elevated temperatures may arise from partial shading of the modules, reverse bias effects, potential-induced degradation (PID), and defects in cell and module architecture. This analysis provides insights into the temperature variations in photovoltaic modules, guiding the development of solutions to mitigate temperature-dependent degradation.

[0173] Figure 11 shows the distribution of hot spot temperatures reported in research literature. For this technology, temperatures that can impact the functionalized crosslinking polymers are of interest.

[0174] Feedback from photovoltaic (PV) recyclers and other stakeholders may provide insights on recycling challenges, purity requirements, and potential market opportunities. These insights may guide efforts to meet market expectations, mitigate risks in manufacturing, and ensure the applicability of ReCLIP polymers in the PV recycling ecosystem.

[0175] Considerations for ReCLIP design and integration may include purity requirements, surface contamination, encapsulant compatibility, and scalability. With respect to purity requirements, desirable purity thresholds for recovered materials, such as less than approximately 100 ppm of contaminants for float glass applications, may inform the design of the recycling process. Surface contamination may be controlled through characterization techniques such as XPS and moisture control to improve recyclability. Glass recycling may be sensitive to impurities, whereas metal recovery may be less sensitive although metal value may depend strongly on purity. With respect to encapsulant compatibility, challenges associated with encapsulant recycling (e.g., EVA, POE, or polyurethane recycling) may inform strategies for ReCLIP polymers to facilitate separation and enhance recovery rates. With respect to scalability, glass size preferences and approaches to circular sourcing of materials may inform scalable solutions. In some embodiments, the ReCLIP may provide facile access to the cell to enable downstreamInternational Patent Application Docket No. 009062.8583.WO00 recycling while facilitating removal of the glass. In some embodiments, the ReCLIP may enable PV glass recovery for recycling or potential direct re-use. ReCLIP may also facilitate investigations of module reliability, since delamination of modules using conventional methods can present significant challenges.

[0176] Figure 12 shows a synthesis of ReCLIP from commercially available starting materials. Amine-PDMS and distilled furfuryl isocyanate may be reacted to make furfuryl-functionalized PDMS (F-PDMS). F-PDMS and bismaleimide may be mixed and heated to create the crosslinked ReCLIP.1H-NMR spectroscopy may be used to confirm reaction success and product purity.

[0177] In some exemplary implementations, functionalized polymers for cross-linking may be prepared, achieving higher than approximately 90% functionalization with spectroscopic verification and a production of greater than approximately 5-gram batches. In some exemplary implementations, greater than approximately 10 grams of ReCLIP may be produced at greater than approximately 80% yield with greater than approximately 90% conversion of target groups.

[0178] In some exemplary implementations, the synthesis may be optimized and repeatable control of the reactions achieved at various scales, e.g., a significant laboratory scale (e.g., 20-gram batches), or a larger scale. For instance, the synthesis of the furfuryl-PDMS precursor may be optimized. Figure 13 shows an optimized lot (e.g., lot #14) and its corresponding1H-NMR spectrum.1H-NMR confirmed complete conversion of the amine-PDMS to furfuryl-PDMS. Additionally, the optimized lot yielded 20-gram of optically clear material. The reaction reached an almost quantitative 100% yield. This 20-gram lot of optically-clear, 100% functionalized furfuryl-PDMS can provide greater than approximately 1500 cm2of functional ReCLIP for prototype package testing, assuming a characteristic test thickness of approximately 100-micrometer layers.

[0179] According to some embodiments, the one-step chemical modification of commercially available amine-PDMS may be simple enough that it can be routinely conducted by operators with basic laboratory training.

[0180] Featured at the bottom of Figure 13 are previous lots of furfuryl-PDMS arranged in sequential order from lot #1 to #13. Variations in lots reflect adjustments over time to remove trace impurities, achieve optical clarity, and scale up the reaction. Lots #5-8 wereInternational Patent Application Docket No. 009062.8583.WO00 made at a 10-gram scale and lots #9-14 were made at a 20-gram scale. In total, well over 100 grams of furfuryl-PDMS were synthesized. Figure 14 shows1H-NMR spectra of lots #11 -13, demonstrating reproducible (approximately) 100% conversion of target groups to the ReCLIP-ready F-PDMS.

[0181] Furan conversion to the Diels-Alder (DA) adduct — the cross-linked state — may be quantified via1H-NMR. Figure 15A illustrates how furan conversion may be determined. The pre-crosslinked spectrum (shown in (a) in Figure 15A) was taken at t=0 minutes and shows two peaks in the range of approximately 6.20-6.70 ppm. These peaks are located at approximately 6.21 and 6.30 ppm and correspond to the two protons opposite to the furan’s oxygen. After 300 minutes at approximately 60°C, a large proportion of these peaks shifted downfield to approximately 6.53 and 6.68 ppm, as shown in (b) in Figure 15A. These peaks correspond to the two protons on the alkene in the DA adduct. By integrating all four peaks in the crosslinked spectrum and dividing the area of the two downfield peaks by the cumulative area of all four peaks, the furan conversion may be determined.

[0182] Figure 15B shows the forward cross-linking of the F-PDMS to the bismaleimide as a function of time, conducted at approximately 60°C in solvent solution. The figure features a ReCLIP formulation with a nominal maleimide to furfuryl (Mal:Fur) ratio of 0.37:1 dissolved in chloroform. As the sample was heated, aliquots were taken, and1H-NMR was run. Figure 15B demonstrates greater than approximately 60% conversion of furans to DA adducts at less than approximately 85°C.

[0183] Figure 15C shows the de-crosslinking reaction as a function of time as monitored by1H-NMR using the same analysis described above. These experiments begin with a fully crosslinked ReCLIP formulation with a nominal Mal:Fur ratio of 0.30:1. The material was optically clear, and1H-NMR revealed no excess bismaleimide in the sample. To carry out this experiment, a glass slide was heated on a hotplate to 80, 120, and 140°C. A thermocouple was used to ensure that the glass was at the correct temperature. A small amount of crosslinked material was then deposited on the glass and after 15, 30, or 60 seconds the material was solvated, and1H-NMR was run.1H-NMR revealed that the material fully de-crosslinks within 15 seconds at approximately 140°C.International Patent Application Docket No. 009062.8583.WO00

[0184] Figure 16 shows that three batches of crosslinked ReCLIP were prepared at a nominal ratio of 0.30:1, with crosslinking percentage (from the conversion of furans) evaluated spectroscopically. After mild heating (less than approximately 85°C) in chloroform, the following crosslinking fractions were achieved: 67.3%, 68.5%, and 63.3%. The material was optically clear, and1H-NMR confirmed negligible free bismaleimide present. The absolute variation in crosslinked fraction was within 66 ± 2.8%, demonstrating batch-to-batch consistency.

[0185] To achieve consistent crosslinking densities and optically transparent films, a calibration curve may be constructed to relate the nominal maleimide:furfuryl (MakFur) ratio to actual MakFur ratios based on1H-NMR. Figure 17A shows that below a nominal MakFur ratio of approximately 0.41 :1 , the crosslinked ReCLIP films may be optically clear as there are enough furan moieties to react with maleimide moieties. ReCLIP polymer made below this threshold may be optically clear. Above this ratio, ReCLIP films may become increasingly opaque as unreacted bismaleimide begins to accumulate. Figure 17B shows another calibration curve indicating that a nominal maleimide-to-furan (MakFur) feed ratio of approximately 0.40 ± 0.04:1 corresponds to a 1 :1 MakFur ratio.

[0186] The compatibility of the ReCLIP with encapsulants may be characterized through systematic interface-by-interface analysis to identify weak links and opportunities for polymer design to address them. Components for laminate fabrication have been sourced, including a laminator, encapsulants (e.g., EVA films, POE films, , or polyurethane films), PV glass and backsheet materials, and solar cells (e.g., 2-inch Si PERC solar cells, both tabbed and untabbed). Figure 18 shows exemplary encapsulants, cells, and PV glass, exemplary sources, along with a research-scale laminator, which may enable packaging within the scope of this technology.

[0187] Figure 19A shows an exemplary laminator. Figure 19B shows preparation of a mini module. Figure 19C shows a prepared mini module laminate.

[0188] To evaluate the adhesion strength of ReCLIP in laminated photovoltaic module stacks, small-area laminate stacks were prepared with Glass / ReCLIP-EVA-ReCLIP / Glass configurations and compared to reference EVA / Cell laminates. From the literature data of Figure 10, the EVA / cell interface is known to be the weakest interface in standard packages. ReCLIP was deposited on glass substrates using a blade coater,International Patent Application Docket No. 009062.8583.WC00 achieving uniform film coverage. Laminates were fabricated using a standard lamination process optimized for compatibility with ReCLIP and EVA. The stacks were prepared on 3x1 inch glass substrates (borosilicate glass), with a layer of EVA and ReCLIP films.

[0189] In some exemplary implementations, peel testing was conducted using a 90° peel test setup, employing an extended backsheet as a pull-tab. To ensure peeling occurred at the desired interface, a Teflon separator was strategically placed in the laminate stack during assembly. Figures 20A-20C show schematics of 90° peel test sample stacks for three interface configurations: an EVA-Backsheet (EVA-BS) configuration with the Teflon separator positioned at the EVA / Backsheet interface (Figure 20A), an EVA-Glass configuration with the Teflon separator positioned at the Glass / EVA interface (Figure 20B), and an EVA-Front Cell configuration with the Teflon separator positioned at the Adhesive / Cell interface (Figure 20C). Each configuration includes layers of glass (I), EVA (II), and backsheet (III). The EVA-Front Cell configuration additionally includes an adhesive layer (IV), a cell (V), and an Al foil backing (VI). The EVA-BS configuration tests the EVA / Backsheet interface, the EVA-Glass configuration tests the Glass / EVA interface, and the EVA-Front Cell configuration tests the EVA / Cell interface. Arrows indicate the relevant interface under test in each configuration. Peel strength was measured on five replicates for each laminate configuration, and averages were calculated.

[0190] The peel strength data showed that the Glass / ReCLIP-EVA interface demonstrated significantly higher adhesion strength compared to the reference Cell / EVA interface. Figure 21 A presents representative peel strength curves of the Glass / ReCLIP-EVA interface and the Cell / EVA interface. The Cell / EVA interface peeled at less than approximately 2 N / mm, while the Glass / ReCLIP-EVA laminate exhibited a peel strength of approximately 4.5 N / mm. Figure 21 B provides a bar chart comparing the average peel strengths of the 5 samples tested in each experimental group. The Cell / EVA interface had an average peel strength of approximately 1.5 N / mm, whereas the Glass / ReCLIP-EVA interface had an average peel strength of approximately 5 N / mm. The ReCLIP-containing laminates not only meet but significantly exceed the adhesion threshold relative to the weakest interface in conventional modules, the Cell / EVA interface.International Patent Application Docket No. 009062.8583.WO00

[0191] Additionally, a comparison with literature data (Figure 10) shows that the peel strength of Glass / ReCLIP-EVA laminates is within range of Glass / EVA interface strengths reported in the literature (approximately 4-13 N / mm) and is stronger than typical Cell / EVA interface values (approximately 1-5 N / mm). These results affirm the potential of ReCLIP to enable facile delamination without sacrificing adhesive strength in PV modules.

[0192] To demonstrate the ability of ReCLIP to enable facile unzipping of photovoltaic package components by reversing crosslinks at elevated temperatures, lap shear strength measurements were conducted on crosslinked ReCLIP samples. The test samples comprised a glass / ReCLIP-EVA / backsheet stack.

[0193] Figure 22 shows a comparison of shear force sustained for ReCLIP in the cross-linked state versus the de-crosslinked state. The lap shear strength of crosslinked ReCLIP samples was measured across six replicates, and the peak elastic force in the initial linear deformation regime was used for comparison. As illustrated in Figure 22, the shear force sustained in the crosslinked ReCLIP samples is over 2,225 times higher than the upper bound of the de-crosslinked state.

[0194] The de-crosslinked samples delaminated under their own weight and may be difficult to test accurately. The upper bound of the de-crosslinked state strength may therefore be approximated as the weight of the EVA / backsheet. This weight, calculated for a 3-inch sample, corresponds to a force of approximately 0.01 N, which was used as a reference for comparison. The results demonstrate that ReCLIP achieves lap shear strengths far exceeding a 10-time reduction in strength between the crosslinked and de-crosslinked states.

[0195] To evaluate the optical performance of ReCLIP-enhanced laminates, the AM1 ,5G-weighted absorbance of ReCLIP-enhanced laminates was compared to standard laminates without ReCLIP. Two laminate configurations were included: Glass / EVA / Glass and Glass / ReCLIP-EVA-ReCLIP / Glass. For each configuration, four replicates were prepared, with transmittance measurements taken at three distinct locations on each sample — top edge, center, and corner — to ensure comprehensive representation of optical performance.

[0196] UV-Vis spectroscopy was employed to measure transmittance (%) over the solar-relevant wavelength range of approximately 300-1200 nm. Using the AM1 ,5G solarInternational Patent Application Docket No. 009062.8583.WO00 spectrum as a reference, the AM1 ,5G-weighted absorbance values were calculated for each laminate type. The AM1 ,5G-weighted absorbance values were averaged across all samples and locations. Figure 23A presents the AM1 ,5G-weighted absorbance comparison. The ratio of AM1 ,5G-weighted absorbance between Glass / ReCLIP-EVA-ReCLIP / Glass and Glass / EVA / Glass laminates is calculated to be approximately 1.18.

[0197] It is noted that this ratio may represent a conservative estimate since the thicknesses of the polymer stacks are not equal, with the ReCLIP laminates utilizing two layers of ReCLIP. Despite this, ReCLIP may be suitable to be used or tested on the front side of photovoltaic packages from an optical clarity perspective.

[0198] To contextualize the technology further, Figure 23B illustrates the transmittance profiles of the best-performing samples from each laminate type. Both laminates demonstrated high transmittance across the solar spectrum, with only minimal differences, reaffirming the compatibility of ReCLIP with standard photovoltaic module designs.

[0199] These results indicate that the ReCLIP-enhanced laminates meet transparency requirements for photovoltaic applications.

[0200] The optical clarity of ReCLIP may be sufficient for frontside application in PV modules, and the reduction in adhesive strength upon de-crosslinking may enable facile module separation. Synthesis of the components of the ReCLIP crosslinking polymers may be scaled up, resulting in batches providing more than approximately 10 grams of material with desirable optical clarity.

[0201] Crosslinking and reverse-crosslinking reactions may be demonstrated using the synthesized polymers. Insertion of the ReCLIP between EVA and glass in laminated test structures may provide desirable optical clarity, mechanical adhesion surpassing the weakest interfaces in modules (e.g., EVA / cell), and programmatic delamination with facile and complete separation outside of terrestrial operating conditions.

[0202] The amount of ReCLIP needed to enable facile delamination may be evaluated, seeking to reduce or minimize material volume and associated cost. The mechanical strength of interfaces in silicon cells with ReCLIP may be tested to further probe the application space. Optimization of the cross-linking density based upon manipulation ofInternational Patent Application Docket No. 009062.8583.WO00 the precursors may be examined in terms of the mechanical and optical properties achieved.III. Example Synthesis and Experimental Methods

[0203] In some embodiments, a reversibly-crosslinking polymer (ReCLIP) may be synthesized from commercially-available precursors. In some exemplary implementations, more than 10 batches at greater than approximately 10-gram scale may be produced in an academic laboratory setting. The polymer synthesis utilizes an isocyanate addition reaction between amine-functionalized PDMS and isocyanate-functionalized compounds to form urea linkages. The reaction may proceed without requiring precious metal catalysts (e.g., platinum or gold), which are commonly needed in other PDMS-type reactions. The metal-free synthesis may achieve approximately 100% atom economy with substantially no side products generated or catalyst poisoning. The synthesis can be performed using environmentally friendly solvents, and both solvents and triethylamine can be recovered for flow reaction and mass production in a single system. This approach may enable high-throughput manufacturing, while simplifying the synthesis process and reducing both costs and material waste.

[0204] The technology enables systematic variation of multiple parameters. The following are exemplary variations that may be employed alone or in combination. The PDMS molecular weight and amine content can be adjusted to control crosslinking density. The amine groups can be substituted with hydroxyls to form urethane instead of urea motifs in the pendant group. The crosslinker architecture can range from two-arm (bismaleimide) to multi-arm (tri-, tetra-, or n-arm) maleimide structures. The linker between maleimide groups can be modified from aromatic to aliphatic structures with variable molecular weight. The linker can incorporate chemical sensory molecules for specific detection capabilities.

[0205] Figure 24 shows an exemplary synthetic scheme for the formation of the reversibly cross-linked interlayer polymer, ReCLIP (compound 5). Furan, maleimide, and urea motifs are highlighted for clarity. The structural differences between the endo and exo Diels-Alder adducts are illustrated, with distinguishing features indicated in the respective insets. The urea functional group is annotated to emphasize its presence and location within the molecular structure. Temperature ranges applicable to both the forwardInternational Patent Application Docket No. 009062.8583.WO00 Diels-Alder reaction and the reverse (retro-Diels-Alder) reaction are provided to show suitable reaction conditions. The urea motifs may form hydrogen bonds and were introduced to increase adhesion. Moreover, this reaction was chosen for its simplicity (one-step), scalability, and the fact that it does not require a precious metal catalyst (e.g., platinum).

[0206] Exemplary materials that may be used include: furfuryl isocyanate (e.g., 97%, Sigma-Aldrich) (compound 1 as illustrated in Figure 24), 2-3% aminopropylmethylsiloxane (e.g., Gelest, AMS-132, 4500-6000 g / mol) (compound 2 as illustrated in Figure 24), bismaleimide (e.g., 95%, Thermo Scientific) (compound 4 as illustrated in Figure 24), tetrahydrofuran anhydrous (>99.9%, e.g., Sigma-Aldrich) (THF), triethylamine anhydrous (>99.5%, e.g., Carolina Chemical) (TEA), hexanes (e.g., Fisher Chemical), and acetonitrile (e.g., Fisher Chemical) (ACN). Chloroform-d (e.g., 99.8 atom% D, Sigma-Aldrich) may be used both as a solvent to cross-link ReCLIP and as a solvent in which to obtain1H-NMR spectra without having to concentrate and redissolve the sample. All glass reaction vessels may be flame-dried under vacuum unless otherwise noted.

[0207] An exemplary optimized synthetic route to compound 3 (as illustrated in Figure 24) is as follows. In some exemplary implementations, to a 250-mL single-neck round bottom flask equipped with a magnetic stir bar and rubber stopper was added 20 g of compound 2 (AMS-132; 8.9 mmol NH2 sites). The flask was then subjected to three cycles of purging with nitrogen and evacuation under high vacuum. THF (150 ml_) and TEA (10 mL, 72 mmol, 8.1 eq. vs NH2) were added. Lastly, distilled compound 1 (1.0 mL, 9.3 mmol, 1.0 eq. vs NH2) was added dropwise. The reaction mixture was then heated to 50°C and mixed at 250 rpm for 24 hours. After the reaction was completed, deionized water (1.0 mL, 55 mmol, 6.0 eq. vs compound 1) was added to the flask to quench any excess isocyanate. The THF and TEA were evaporated leaving behind a viscous pearlescent semisolid.

[0208] A liquid-liquid extraction of compound 3 with hexanes and ACN was carried out. First, hexanes (200 mL) and ACN (50 mL) were added to the flask and the solution was stirred at 400 rpm for 1 hour. The mixture was then transferred to a 250 mL separatory funnel. The separatory funnel was shaken vigorously; then the mixture wasInternational Patent Application Docket No. 009062.8583.WO00 allowed to settle for 3 hours. The hexane (top) layer contained compound 3 and the ACN layer (bottom) contained the impurities. The hexane layer was transferred to another 250 mL single-neck round bottom flask. The hexanes were evaporated, leaving behind compound 3, a clear oily liquid. Compound 3 was then transferred to a 20 mL scintillation vial and volatiles were removed overnight in a vacuum chamber.1H-NMR was performed to confirm successful synthesis and purification.

[0209] In some embodiments, distillation of compound 1 (furfuryl isocyanate) may be performed prior to use. Without distillation, compound 3 may exhibit a yellow tint, which may diminish ReCLIP’s appeal as an optically transparent adhesive. According to some embodiments, the one-step chemical modification of commercially available amine-PDMS may be simple enough that it can be routinely conducted by operators with basic laboratory training.

[0210] 1H-NMR confirmed the successful formation and purity of the ReCLIP precursor (compound 3) (Figure 25A and Figure 26). The absence of a resonance at 2.65 ppm indicated full conversion of the terminal amine in compound 2. The resonance at 4.53 ppm was assigned to water hydrogen-bonded with the urea motif. Figure 25B shows a 20-mL vial of compound 3.

[0211] Panels (A) and (C) of Figure 27 show the1H NMR spectra and skeletal structures of compound 1 after and before distillation, respectively. Before distillation, the spectrum contained extra resonances, indicating the presence of impurities. Panels (B) and (D) of Figure 27 show photographs of compound 1 after and before distillation, respectively. The undistilled compound 1 appeared amber-colored, while the distilled product was clear. Without distillation, compound 3 may exhibit a yellow tint, which may diminish ReCLIP’s appeal as an optically transparent adhesive. Panel (E) of Figure 27 shows the1H NMR spectrum and skeletal structure of compound 4. Panel (F) of Figure 27 shows a photograph of compound 4.

[0212] Figure 28 shows how optically clear the material was from the start of the reaction to the liquid-liquid extraction. Panel (A) of Figure 28 shows the reaction flask filled with compound 2, THF, TEA, and distilled 1 before heating. Panel (B) of Figure 28 shows the reaction flask after heating for 24 h at 50 °C. The solution remained mostlyInternational Patent Application Docket No. 009062.8583.WO00 clear, with a slight haziness that was caused by impurities, which were removed via liquid-liquid extraction with hexanes and ACN (panel (C) of Figure 28).

[0213] To further confirm the formation of the urea in compound 3 and the DA adduct in compound 5, FTIR may be performed (Figures 29A and 29B). ATR-FTIR spectra were collected with a Fourier transform infrared spectrometer (e.g., Nicolet iS50) fitted with a diamond attenuated total reflectance attachment (e.g., Smart-iTR). Spectra were recorded at room temperature. Figure 29A shows absorption bands characteristic of the PDMS backbone at 2962 / 2905 cm-1 (C-H stretching, asymmetric / symmetric), 1413 / 1257 cm-1 (C-H bending, asymmetric / symmetric), 1065 / 1009 cm-1 (Si-O-Si stretching, asymmetric / symmetric), and 785 crrr1(Si-C stretching, asymmetric). Figure 29B shows the absorbance between 1800-1500 cm-1with key absorption bands assigned to the urea (1635 and 1577 cm-1) and the DA adduct (1774 and 1713 cm-1), indicating successful synthesis of compound 3 and compound 5. The absorption band at 1513 cm-1is assigned to the phenyl of compound 4.

[0214] To confirm that the backbone remained intact following installation of furan on pendant amines, Gel Permeation Chromatography (GPC) was performed on compounds 2 and 3 (Figure 30). GPC was performed using a separation module (e.g., Agilent 1260 Infinity II) equipped with a refractive index detector (e.g., 1260 Refractive Index Detector) and a ResiPore column, eluting with chloroform at 1 mL / min at 35°C. Molecular weights were calculated relative to linear polystyrene (PS) standards. GPC of compound 2 (as supplied by e.g., Gelest) and compound 3 resulted in Mn= 5.51 kDa, Mw = 6.03 kDa, D = 1.09 and Mn= 5.71 kDa, Mw = 6.04 kDa, D = 1.06, respectively, indicating the nondestructive nature of the furan-functionalization reaction. D = Mw / Mn.

[0215] Figure 31 shows results of13C-NMR (150.9 MHz, CDCh) performed on the two synthesized molecules, compounds 3 and 5.

[0216] Some embodiments relate to a method to distinguish between the endo and exo diastereomers after characterizing the starting materials, as these may impact the thermal stability of ReCLIP in the cross-linked state. 2D NMR experiments may be used to resolve overlapping resonances and unambiguously assign the diastereomeric adducts (Figures 32A-32F).International Patent Application Docket No. 009062.8583.WO00

[0217] In some exemplary implementations, to prepare a model system for the identification of1H-NMR resonances, 167.7 mg of compound 4 (0.4680 mmol, 0.9360 mmol maleimide groups) was added to a 4 ml_ vial. Next, 263.6 mg of distilled compound 1 (2.141 mmol, 2.288 eq. vs maleimide groups) was added, along with 3 ml_ of CDCIs. The solution was vortexed for 20 seconds, then heated in an oil bath for 2 hours at 40°C. An aliquot was taken after 2 hours for 1 D and 2D COSY1H-NMR analysis. Using this model system, NMR data was acquired that helps characterize the crosslinking reaction. Specifically, 2D1H-NMR was used to determine which peaks correspond to which protons on the Diels-Alder adduct. This information, which enables distinction between the endo and exo adducts, provides insight into the thermal properties of the resulting Diels-Alder crosslinked polymeric material.

[0218] Figures 32A-32F present 1D and 2D1H-NMR analyses used to distinguish between the endo and exo configurations of the Diels-Alder adducts. Figure 32A shows the skeletal structure of compounds 4 and 1 with key protons named. Figures 32B and 32C show the 3D skeletal structures of the endo and exo isomers, respectively, with all 10 protons highlighted and named. Figure 32D shows1H-NMR of the reaction product with the 10 resonances associated with the DA adduct labeled. Figure 32E shows 2D1H-1H COSY NMR featuring Fb.exo + Fa.exo and Fb.endo + Fa, endo cross peaks. Figure 32F shows 2D1H-1H COSY NMR featuring Ma-2,endo + Fa, endo cross peaks.

[0219] The first set of resonances in the range of 6.4-6.7 ppm was assigned to the two protons on the newly formed alkene of the DA adduct (Fb and Fc). The second set of resonances in the range of 5.4-5.5 ppm was assigned to the bridgehead proton (Fa). The last set of resonances, furthest upfield, between 3.0-3.9 ppm, were assigned to the new methine protons originating from the maleimide (Ma-1 and Ma-2).

[0220] To further differentiate between the protons of the endo and exo adducts, 2D NMR spectroscopy was employed. Analysis of the resulting spectra demonstrated a cross-peak at 3.85 ppm I 5.43 ppm indicating that the new methine proton at 3.85 ppm correlates with the bridgehead proton, Fa, at 5.43 ppm (Figure 32E). The resonance at 3.85 ppm was thus assigned as Ma-2, endo since the existence of this cross-peak is only possible in the endo adduct. There was no correlation between Ma-i,exo and the bridgehead proton, Fa, exo, as a result of the approximately 90° dihedral angle between theInternational Patent Application Docket No. 009062.8583.WO00 two protons. After assigning the Ma-2,endo resonance and integrating it to approximately 1 , the other endo resonances were assigned starting with the Ma-i,endo resonance at 3.47 ppm, followed by the two endo resonances on the newly formed alkene of the DA adduct viz. Fb.endo and Fc.endo between 6.4-6.7 ppm. The Fa,endo resonance and Fa,exo resonance partially overlapped; however, the Fa,endo resonance is slightly more upfield.

[0221] To distinguish between the Fb and Fcprotons, the 2D NMR spectrum was similarly analyzed (Figure 32F). The presence of two cross-peaks at 6.68 ppm 15.43 ppm and 6.65 ppm / 5.43 ppm helped distinguish between the Fb protons from Fc protons as the Fb protons were the only ones that correlate with the bridgehead proton, Fa. The Ma-i.exo and Ma-2,exo resonances were assigned upon analogy to a study by others which had Ma-i,exo and Ma-2,exo resonances that appeared at 3.16 and 3.08 ppm, respectively. The unlabeled resonance between Fc.exo and Fc.endo is likely a signal originating from hydrogen bonding of the urea.

[0222] Figure 33 shows equations for quantitative determination of maleimide and furan conversion and exo content. The set of equations can be used to calculate the extent of maleimide and furan conversion as well as the percentage of exo adduct formation. These calculations are based on the peak integrations from the1H-NMR spectra. Equation (1) can be used to calculate normalized furan conversion. Equation (2) can be used to calculate exo percentage from furan peaks. Equation (3) can be used to calculate normalized maleimide conversion. Equation (4) can be used to calculate exo percentage from maleimide peaks. Panel (A) at the bottom of Figure 33 shows stacked 1 D1H-NMR of ReCLIP crosslinking with key peaks labeled. Stacked NMR spectra over time demonstrate dynamic changes in adduct composition during crosslinking. These data provide the quantitative basis for optimizing reaction conditions and confirm the synthetic scheme’s rationale for promoting exo over endo adducts to enhance thermal robustness.

[0223] In some exemplary implementations, NMR spectra may be collected at 300 K using a 600 MHz spectrometer (e.g., Bruker Avance III) fitted with a 1.7 mm triple resonance cryoprobe or a 5 mm broadband room-temperature probe, both employing inverse detection and z-axis gradients. For instance, to prepare samples, 2-10 mg of material were added to a microcentrifuge tube. The material was then dissolved inInternational Patent Application Docket No. 009062.8583.WO00 approximately 1 ml_ of CDCI3 and vortexed. 40 pL of solution was transferred to 1.7 mm NMR tubes while 500 pL of solution was transferred to 5 mm NMR tubes. To slow the forward reaction, samples related to reaction progression studies were transported to the NMR facility in a cooler packed with dry ice.1H-NMR (minimum 64 scans; 0.5 s relaxation delay) and13C-NMR (2,500 scans; 5 s relaxation delay) spectra were apodized with 1 Hz exponential line broadening prior to Fourier transformation. 2D NMR experiments used 16 scans with a 1 s relaxation delay.

[0224] In some exemplary implementations, TGA thermograms may be collected using a DSC / TGA instrument (e.g., TA Instruments Discovery SDT 650). For instance, samples of compound 3 (e.g., 28 mg) and compound 4 (e.g., 9 mg) were placed in ceramic crucibles and heated from 30-600°C under ambient conditions. For better resolution, a ramp rate of 5°C / min was utilized.

[0225] Figure 34 presents thermogravimetric analysis (TGA) of the individual components used in the crosslinked material. The TGA was conducted using a ramp rate of 5°C / min. The F-PDMS component (compound 3), which contains the urea motif, exhibited an onset of degradation (Ts%) at approximately 241 °C. In contrast, the bismaleimide component (compound 4) remained thermally stable up to approximately 482°O. These thermal degradation profiles inform the temperature limits for processing and application of the resulting crosslinked material. Of the two components of ReCLIP, the furan-functionalized PDMS (compound 3) is less thermally stable than the bismaleimide (compound 4). However, compound 3 may still withstand temperatures up to 241 °C, well above temperatures required to de-cross-link the cured material (i.e., approximately 90-150°C). In other words, the de-crosslinking temperatures are non-degradative.

[0226] To ensure precision and thorough mixing, the bismaleimide was first dissolved in a 10 mM stock solution using chloroform then mixed with compound 3 to make ReCLIP. Figure 35A shows a calibration curve with 95% confidence band that relates wt. % of bismaleimide to actual MakFur ratio based on the ratio of the integral of Mato the integral of Fb plus Fcin a1H-NMR spectrum taken at to. A 2.78 ± 0.23 wt. % bismaleimide content equates to an actual 1 :1 MakFur ratio. When making samples, the goal was to get as close to a stoichiometric ratio as possible without going over, since excess compound 4International Patent Application Docket No. 009062.8583.WO00 in the formulation would lead to opaque films, as evidenced by Figure 35B. Figure 35B shows an array of ReCLIP formulations with increasing amounts of compound 4.

[0227] To investigate the reaction progress of the reverse (retro-DA) reaction, ReCLIP was fully cured in a vial at 80°C. A few milligrams of cured material were then placed onto a hot plate equipped with a thermocouple at 70°C. After 1 minute, the material was redissolved in CDCIs and frozen on dry ice to slow the forward reaction. The process was repeated for temperatures of 80 to 140°C in increments of 10°C.1H-NMR samples were prepared, and spectra were obtained using the same conditions and parameters described above. Variable-temperature1H-NMR (VT1H-NMR) was not used for these experiments as the intent was to observe how ReCLIP would de-cross-link (dissociate) in the solid state.

[0228] To prepare a ReCLIP sample at a 1 :1 maleimide:furan (Mal:Fur) ratio, 1.5 g of compound 3 was added to a 20 mL vial. Next, 17.8 g (approximately 11.9 mL) of a 10 mM stock solution containing compound 4 dissolved in CDCI3 was added. The solution was vortexed for 15 seconds then heated to 60°C on a hotplate for approximately 10 hours at which point an aliquot was taken for1H-NMR. This aliquot was used as a “day 0” data point. By gradually evaporating the solvent just below its boiling point, the material cross-linked partially and afforded sufficient viscosity for blade coating. 80 pL of ReCLIP was then deposited on a clean 25 mm x 25 mm glass slide and blade coated at a speed of 32.5 mm / s with a blade height of 350 nm.

[0229] Glass slides of 25 mm x 25 mm were cleaned by sonicating them for 15 minutes in MilliQ water, acetone, and isopropanol. After cleaning, they were plasma treated for 10 minutes and immediately used for preparation of lap shear samples. The ReCLIP-coated glass was then immediately placed on a 60°C hot plate for 6 minutes before the second piece of glass was placed on top. A set of glass-ReCLIP-glass stacks were compressed under approximately 10 kPa of force and cured for 14 days at 60°C.

[0230] Lap shear tests were performed with an extensiometer (e.g., Mark-10) operated in the vertical direction at room temperature. This extensiometer was equipped with a 100 N force gauge and custom 3D-printed polycarbonate grippers. Additionally, for maximum adhesion between the grippers and glass-ReCLIP-glass stacks, polyimide tape was wrapped around the grippers and the contact points on the stacks. The grippers wereInternational Patent Application Docket No. 009062.8583.WO00 then clamped onto the contact points and the assembly (i.e., the grippers and stack) was carefully installed into the extensiometer. The samples were then sheared at a rate of 1.4 mm / min. Load (N) was measured as a function of travel (mm). Shear strength was calculated by taking the max load (N) and dividing it by the overlapping area of the two glass slides, usually approximately 330 mm2.

[0231] Figure 36A shows an example of a glass-ReCLIP-glass stack cured at 60°C for 14 days. Figure 36B provides a schematic diagram of the lap-shear geometry used to measure the strength of the bonds.

[0232] Samples sheared on day 14 were placed on a 150°C hot plate for 2 minutes to liquify ReCLIP. The two glass substrates were then recombined and compressed under a 1 kg steel block for 10 minutes at room temperature. This allowed ReCLIP to re-cross-link slightly before being placed on a 60°C hot plate overnight. Lap shear tests were then performed the same way as described above.

[0233] Optical transmittance was evaluated using UV-Vis-NIR spectroscopy by coating the ReCLIP polymer on a glass substrate. The refractive index of ReCLIP closely matches that of glass, reducing interfacial reflection. Total hemispherical transmittance of glass, glass-glass, and glass-ReCLIP-glass stacks (25 mm x 25 mm) was measured after curing the ReCLIP layer for 14 days, matching the processing and curing conditions used for lap shear tests. Transmittance measurements were recorded within the 300-1100 nm wavelength range using a double-monochromator spectrophotometer (e.g., PerkinElmer Lambda 1050) equipped with a 150 mm InGaAs integrating sphere.

[0234] Optical micrographs were taken with a microscope (e.g., Leica DM2700M) at 5x magnification in transmission mode.

[0235] ReCLIP’s delamination functionality was evaluated through time-lapse experiments conducted on a glass / ReCLIP / glass stack. ReCLIP was crosslinked, rendering the stack adhesive. The delamination process was triggered by an external stimulus (e.g., heat) outside terrestrial operating conditions and the resulting deadhesion was investigated.

[0236] Glass / ReCLIP-EVA laminates were fabricated and subjected to peel and lap shear tests to assess adhesion and delamination performance. Following theInternational Patent Application Docket No. 009062.8583.WC00 methodologies described in studies by others, adhesion strength was quantified using force-displacement curves.

[0237] ReCLIP may be deposited substantially uniformly using a blade coater, achieving substantially homogeneous coverage and consistent thickness. Laminates may be fabricated using standard encapsulants (e.g., EVA) and components (e.g., glass, backsheet), demonstrating seamless integration into existing PV manufacturing workflows.IV. Example Results

[0238] Figures 37A-37I show time-dependent conversion monitored by1H-NMR of the formation of the exo and endo products during the cross-linking of ReCLIP at different temperatures: Figures 37A-37C at 50°C, Figures 37D-37F at 60°C, and Figures 37G-37I at 80°C. Figures 37A, 37D, and 37G show the forward reaction monitored by1H-NMR. Figures 37B, 37E, and 37H show the exo proportion monitored by1H-NMR. Figures 370, 37F, and 37I show the optical transparency of ReCLIP prepared at corresponding temperatures. Films were held up to a white light source to demonstrate optical transparency and clarity when adhered to the bottom of a glass scintillation vial. Error bars represent standard deviation.

[0239] With the endo and exo isomers assigned, the influence of temperature on the bulk reaction progress was investigated. This information was essential in optimizing curing conditions to ensure consistent blade coating of ReCLIP films for mechanical testing. Figures 37A-37I illustrate the evolution of the DA cross-linking reaction in ReCLIP over time, starting with approximately 300 mg of compound 3 in a vial. After approximately 5 hours at 50°C, conversion reached approximately 51% (Figure 37A). To accelerate the extent of cross-linking, the vials were heated to 80°C for 48 hours, which accelerated the progress of the reaction toward completion (Figures 38A-38C). After approximately 5 hours at 60°C, conversion reached approximately 81% due to slowing of the forward reaction upon evaporation of the solvent (Figure 37D). Curing at 80°C proved to be the fastest route to cross-link films: full conversion happened within approximately 3 hours (Figure 37G). Despite this result, heating to 60°C offered a more controlled approach, as this temperature was just below the boiling point of chloroform, allowing for more gradual evaporation and more time to blade coat.International Patent Application Docket No. 009062.8583.WC00

[0240] Another important detail for blade coating was the relatively large vertical error bars at approximately 5 hours (Figure 37A), approximately 3 hours (Figure 37D), and at approximately 0.5 hours (Figure 37G). The larger standard deviations at intermediate time points are attributed to solvent loss via evaporation, which renders the formulation more sensitive to small changes in temperature and concentration. At this point, the material became viscous enough to blade coat.

[0241] Figures 38A-38C show ReCLIP cured at 50°C for 5 hours and then 80°C for 48 hours. Figure 38A shows the ReCLIP solution before heating. Figures 38B and 38C show the forward reaction tracked via1H-NMR. Error bars represent standard deviation.

[0242] Figures 37B, 37E, and 37H display time-dependent exo adduct proportions for ReCLIP at 50, 60, and 80°C, respectively. Over approximately 5 hours at 50°C, the exo proportion only reached approximately 41%. At higher temperatures, the exo content increased rapidly, reaching approximately 53% at 60°C and approximately 83% at 80°C within the same 5-hour time frame. This trend is summarized in Figure 39. Furthermore, a closer look at Figures 37E and 37H revealed an initial rise in exo content during the first hour, before stabilizing.

[0243] Figure 39 shows ReCLIP’s exo proportion based on1H-NMR after approximately 5 hours at 50, 60, and 80°C. Error bars represent standard deviation.

[0244] Minor discrepancies between the exo proportion calculated from furan- and maleimide-derived resonances arose from two limitations of the1H-NMR data: (1) the Ma-i.endo resonance was sometimes obscured by noise, leading to an overestimate of the exo proportion and (2) the possible urea hydrogen-bonding resonance at 6.49 ppm overlapped with the Fc.endo resonance, leading to an overestimate of the endo proportion. The Ma-2,endo and Fa signals were unsuitable alternatives because they overlapped with other signals in the1H-NMR spectrum. The true exo proportion is likely somewhere between the two extremes (i.e., the exo proportion based on the furan resonances is the lower bound while the exo proportion based on the maleimide resonances is the upper bound). It should also be noted that variable-temperature1H-NMR (VT1H-NMR) was not possible for these experiments since TCE-d, a higher-boiling point alternative to CDCI3, was not a good solvent for ReCLIP and the reaction would not go to completion without the solvent evaporating.International Patent Application Docket No. 009062.8583.WO00

[0245] Figure 37C shows the material cured at the bottom of a vial after heating (film thickness approximately 2.5 mm). Figures 37F and 371 show the optical transparency of films cured overnight at 60 and 80°C, respectively. These films were not used for1H-NMR measurements and required approximately 1.5 g of compound 3. They are shown undamaged and pristine with a thickness of approximately 4-5 mm.

[0246] Thermal reversibility was evaluated by monitoring the temperature-dependent retro-DA of ReCLIP with1H-NMR. Figures 40A and 40B show temperature-dependent de-cross-linking (dissociation) behavior monitored by1H-NMR after 1 minute. Figure 40A shows the change in furan / maleimide conversion. Figure 40B shows the relative exo adduct (conversion x exo fraction).

[0247] The onset of dissociation was observed at approximately 90°C (Figure 40A), which is consistent with several reports in the literature. However, there was a significant drop in conversion (i.e., a spike in dissociation) between approximately 110-120°C, indicating that the retro-DA pathway dominated and even the exo adduct began to dissociate at these temperatures (Figure 40B).

[0248] Figures 41A-41 E demonstrate the ability of the material to function as a reversible and optically transparent adhesive. Figure 41 A shows the shear strength of glass-ReCLIP-glass stacks cured at 60°C. n = 1 for days 1 and 3; n = 3 for days 5, 7, 14, and the debond-rebond cycle. Error bars represent standard deviation. Figure 41 B shows UV-Vis-NIR transmittance spectra.

[0249] Figure 41 A shows the shear strength of glass-ReCLIP-glass stacks cured at 60°C for 1 -14 days (i.e., the samples were continuously heated at 60°C for up to 14 days). The gradual increase in shear strength was likely due to the elimination of air bubbles as the material settled. On day 5, shear strength was 137 ± 6 kPa, which was 74% of the shear strength of 184 ± 35 kPa achieved on day 14. Shear strength could be improved further via a debond-rebond cycle after 14 days, which pushed the shear strength to 286 ± 50 kPa. The increase in variability was likely due to moisture ingress and other contaminants, leading to heterogeneity in the cross-link density. Figures 42A and 42B show reaction progress data corresponding to Figures 41 A and 41 B for these postsheared films. Figure 43 shows optical micrographs and photographs of post-shear films corresponding to Figures 41 A and 41 B.International Patent Application Docket No. 009062.8583.WO00

[0250] A shear strength of 286 ± 50 kPa is comparable in magnitude to commercially available silicones. For instance, a study by others measured a shear strength of 133— 257 kPa for Sylgard 184 films (2-4 mm thick). Additionally, other studies reported shear strengths of 380 kPa and approximately 490 kPa, respectively, for other vinyl-terminated PDMS systems. ReCLIP’s shear strength could be improved by optimizing blade coating parameters, such as lowering blade height and speed, to produce uniform, bubble-free films with straight edges. Replacing chloroform with a less volatile solvent and curing stacks in a vacuum oven could also minimize voids and air bubbles. Additionally, increasing compression pressure during curing and raising cross-linking density through higher furan functionality and bismaleimide concentration may further enhance adhesion.

[0251] Figure 41 C shows the exo adduct proportion as a function of curing time, with the exo proportion reaching approximately 93% by day 5 based on maleimide resonances. The exo proportion based on furan resonances reached approximately 89% over the same period.

[0252] Figure 41 D shows an example of a cured glass-ReCLIP-glass stack after 2 weeks at 60°C prior to shear testing. Figure 36B provides a schematic of the shear test setup. The adhesive was cured between glass slides separated by Kapton tape spacers. After the initial post-cure shear testing, samples were heated to 150°C for 2 minutes to induce debonding of the adhesive. The glass slides were then realigned and heated to 60°C to allow the ReCLIP material to reform crosslinks, enabling a rebonding cycle. Figure 41 E shows an example of a glass-ReCLIP-glass stack prepared for shear testing following the debond-rebond procedure described in Figure 41 A.

[0253] Crosslinked ReCLIP laminates exhibited a peak elastic force of approximately 37.5 N, over 2,225 times higher than the upper bound strength of de-crosslinked samples (0.01 N). This confirms the robustness of ReCLIP during operation and its drastic reduction in adhesion upon decrosslinking.

[0254] Comparison of UV-Vis-NIR transmittance spectra through glass, glass-glass, and glass-ReCLIP-glass stacks (Figure 41 B) demonstrated the advantages of employing the ReCLIP adhesive. The bare glass substrate exhibited an average transmittance of approximately 92% across the wavelength range from 400-1100 nm. The glass-ReCLIP-glass stack closely matched this performance, averagingInternational Patent Application Docket No. 009062.8583.WC00 approximately 90% over the same range, indicating minimal optical losses attributable to the ReCLIP interlayer. In contrast, the glass-glass stack without any interlayer demonstrated notably lower transmittance (approximately 83%). This decrease was attributed to reflective losses arising from the air gap between the two glass layers, confirming the optical benefits of employing ReCLIP.

[0255] After each shear test (days 1-14),1H-NMR was performed. Figure 42A shows that cross-linking (i.e., conversion) was complete by day 1. Furthermore, the material remained fully cross-linked after two weeks. Figure 42B shows that exo proportion reached a maximum of approximately 93% on day 5. Approximately 93% exo appears to be the thermodynamic limit for this system if given enough time to cure, which is consistent with the results of a study by others that showed a 90% exo proportion for a system similar to ReCLIP.

[0256] Panels A and B of Figure 43 show optical micrographs of the post-shear fracture surfaces. The cured film exhibited a flowery, mosaic topography, whereas the debond-rebond film exhibited pronounced striations. Such striations are characteristic of plastic flow and stable crack advance in polymeric adhesives and are consistent with a ductile, cohesive failure mode accompanied by higher shear strength. Panels C and D of Figure 43 show back-illuminated photographs of the same films to enhance contrast and reveal voids. The cured film showed non-uniform coverage, suggesting limited wetting / spread of ReCLIP; this is attributed to partial cross-linking during chloroform boil-off, which elevated viscosity, suppressed flow, and reduced conformability to the glass. In contrast, after liquifying ReCLIP at 150°C the debond-rebond sample wetted and conformed uniformly, yielding a continuous film. Across both conditions, the presence of adhesive residue on the glass indicates a predominantly cohesive failure within the adhesive rather than interfacial (i.e., adhesive) failure.

[0257] Glass / ReCLIP / Glass samples achieve transmittance levels comparable to single glass, with minimal additional reflection losses (Figures 44A and 44B). ReCLIP is transparent with an index of refraction closely matching that of PV glass. It has high transmittance across the visible spectrum and well into the infrared. This optical compatibility ensures that integrating ReCLIP does not compromise the efficiency of PVInternational Patent Application Docket No. 009062.8583.WO00 modules. Instead, it may enhance performance by reducing interfacial reflection, a key contributor to energy losses in conventional modules.

[0258] Figure 44A shows a transmittance spectra comparison of single glass, Glass-Glass, and Glass / ReCLIP / Glass stack. Figure 44B shows a Glass / ReCLIP / Glass stack demonstrating transparency. Figure 440 shows a Glass / ReCLIP-EVA-ReCLIP / Glass laminate showcasing compatibility with PV components.

[0259] The AM1 ,5G-weighted absorbance of Glass / ReCLIP-EVA-ReCLIP / Glass laminates was approximately 1.18 times that of Glass / EVA / Glass laminates.

[0260] Peel strength tests were conducted on a Glass / ReCLIP-EVA / Backsheet stack to evaluate the adhesion at the Glass / ReCLIP-EVA interface. First results demonstrate comparable adhesion for practical application but are slightly lower than those of conventional Glass / EVA stacks, which typically exhibit peel strengths in the range of 8-12 N / mm (Figures 45A and 45B).

[0261] Figure 45A shows peel strength for the Glass / ReCLIP-EVA interface. Figure 45B shows adhesion strength comparison with the Glass / EVA interface. These initial results reflect the unoptimized nature of the ReCLIP formulation and coating process. The peel strength may be adjusted, e.g., enhanced, according to application needs and / or industrial benchmarks.

[0262] ReCLIP-containing laminates (e.g., Glass / ReCLIP-EVA) demonstrated adhesion strengths significantly exceeding the weakest standard PV interface (Cell / EVA, approximately 1 N / mm). Average peel strength for ReCLIP laminates was greater than 3.5 N / mm.

[0263] ReCLIP demonstrates reliable delamination under controlled conditions outside PV operating conditions, confirming its potential to address end-of-life challenges in PV modules. ReCLIP laminates may be heated to elevated temperatures, resulting in easy manual separation of components due to decrosslinking. Still frame images from the delamination experiments capture the progressive separation of PV module components (Figures 46A-46D). At the beginning of the test, the glass-ReCLIP-glass samples are adhered. After the application of the stimulus, the two glass sheets can be separated using the force applied by a pair of handheld tweezers. The process left behind cleanInternational Patent Application Docket No. 009062.8583.WO00 glass surfaces with minimal residue, confirming the suitability of ReCLIP for efficient material recovery.

[0264] Figures 46A-46D show a time-lapse of Glass-ReCLIP-Glass stack delamination process. Figure 46A shows crosslinked ReCLIP stack exhibiting inseparability at t = 0. Figure 46B shows onset of decrosslinking at t = (approximately) 45 seconds. Figure 46C shows ReCLIP decrosslinked, enabling clean separation at t = (approximately) 50 seconds. Figure 46D shows complete delamination achieved at t = (approximately) 55 seconds, demonstrating ReCLIP’s functionality for material recovery. This thermal reversibility underscores ReCLIP’s potential to bridge the gap between recycling efficiency and module performance, offering a sustainable solution for PV waste.

[0265] Figure 47 is a flowchart illustrating a process of preparing a thermally reversible cross-linked polymer, according to some embodiments of the present technology. The method 4700 includes providing (4710) an amine-functionalized polysiloxane. The process 4700 includes reacting (4720) the amine-functionalized polysiloxane with an isocyanate-functionalized compound comprising a diene moiety to form a diene-functionalized polysiloxane comprising pendant diene moieties connected to the polysiloxane backbone through urea linkages. The process 4700 includes combining (4730) the diene-functionalized polysiloxane with a crosslinker comprising two or more dienophile moieties. The process 4700 includes heating (4740) the combination at a first temperature to form reversible crosslinks between the diene moieties and the dienophile moieties through, e.g., Diels-Alder cycloaddition.

[0210] In some embodiments, the amine-functionalized polysiloxane comprises amine-functionalized polydimethylsiloxane (PDMS). In some embodiments, the isocyanate-functionalized compound comprising a diene moiety comprises furfuryl isocyanate. In some embodiments, the furfuryl isocyanate is distilled prior to the reacting 4720.

[0211] In some embodiments, the reacting in 4720 is performed in the presence of a base catalyst. In some embodiments, the base catalyst comprises triethylamine. In some embodiments, the reacting in 4720 is performed in a solvent comprising dichloromethane. In some embodiments, the reacting in 4720 proceeds without requiring precious metal catalysts, achieving approximately 100% atom economy with no side products generated.International Patent Application Docket No. 009062.8583.WO00

[0212] In some embodiments, the crosslinker in 4730 comprises a bismaleimide. In some embodiments, the bismaleimide comprises 1 ,1’-(methylenedi-4,1-phenylene)bismaleimide. In some embodiments, the crosslinker is dissolved in a solvent to form a stock solution prior to combining with the diene-functionalized polysiloxane.

[0213] In some embodiments, the first temperature in 4740 is from approximately 50°C to approximately 80°C. In some embodiments, the heating in 4740 is performed for a duration sufficient to achieve at least approximately 50% conversion of the diene moieties. In some embodiments, full conversion is achieved within approximately 3 hours at approximately 80°C.

[0214] In some embodiments, the reversible crosslinks formed in 4740 comprise endo and exo diastereomeric adducts. In some embodiments, the exo diastereomeric adducts constitute at least approximately 50% of the total adducts. In some embodiments, the exo proportion reaches approximately 83% when heated at approximately 80°C for approximately 5 hours.

[0215] In some embodiments, the process 4700 further comprises, after 4720 and before 4730, purifying the diene-functionalized polysiloxane by liquid-liquid extraction. In some embodiments, the liquid-liquid extraction comprises washing with hexanes and acetonitrile to remove unreacted starting materials and byproducts.

[0216] In some embodiments, the process 4700 further comprises blade coating the combination onto a substrate prior to or during the heating in 4740. In some embodiments, the substrate comprises glass. In some embodiments, the resulting thermally reversible cross-linked polymer is optically transparent.

[0266] Figure 48 shows a process of recycling a photovoltaic module, according to some embodiments of the present technology. The process 4800 includes providing (4810) a photovoltaic module comprising a first substrate, a second substrate, an encapsulant material disposed between the first substrate and the second substrate, and a layer of a thermally reversible cross-linked polymer disposed between the encapsulant material and at least one of the first substrate or the second substrate. The process 4800 includes heating (4820) the photovoltaic module to a de-crosslinking temperature sufficient to break reversible crosslinks in the thermally reversible cross-linked polymer.International Patent Application Docket No. 009062.8583.WO00 The process 4800 includes separating (4830) at least one of the first substrate or the second substrate from the encapsulant material.

[0267] In some embodiments, the thermally reversible cross-linked polymer comprises reversible Diels-Alder crosslinks formed between diene moieties and dienophile moieties. In some embodiments, the diene moieties comprise furan groups and the dienophile moieties comprise maleimide groups. In some embodiments, the reversible crosslinks comprise endo and exo diastereomeric adducts, wherein the exo adducts constitute at least approximately 50% (e.g., 75%, 80%, 90%) of the total adducts after curing.

[0268] In some embodiments, the de-crosslinking temperature in 4820 is from approximately 90°C to approximately 150°C. In some embodiments, a significant drop in conversion occurs between approximately 110-120°C, indicating that the retro-Diels-Alder pathway dominates at these temperatures. In some embodiments, the heating in 4820 is performed for a duration of approximately 1 to 5 minutes.

[0269] In some embodiments, the separating in 4830 comprises manually separating the first substrate or the second substrate from the encapsulant material with minimal mechanical force. In some embodiments, the separating leaves behind substantially clean surfaces with minimal residue, confirming suitability for efficient material recovery. In some embodiments, high-purity recovery of glass, silicon cells, and metals is achieved.

[0270] In some embodiments, the process 4800 further comprises, after the separating in 4830, re-combining the first substrate or the second substrate with the encapsulant material and heating to a crosslinking temperature to re-form the reversible crosslinks, thereby enabling a debond-rebond cycle. In some embodiments, the crosslinking temperature is from approximately 50°C to approximately 80°C. In some embodiments, the debond-rebond cycle results in increased shear strength compared to the initial cured state.

[0271] In some embodiments, the first substrate and the second substrate each comprise glass. In some embodiments, the encapsulant material comprises ethylene vinyl acetate (EVA) or polyolefin elastomer (POE). In some embodiments, the thermally reversible cross-linked polymer is optically transparent with a refractive index that substantially matches that of the first substrate or the second substrate.International Patent Application Docket No. 009062.8583.WO00

[0272] In some embodiments, the layer of the thermally reversible cross-linked polymer exhibits a shear strength of at least approximately 100 kPa in the cross-linked state during operation and transitions to a shear strength of no more than approximately 0.05 kPa in the de-cross-linked state after 4820, representing a reduction in adhesion of greater than approximately 2,000 times.EXAMPLES

[0273] Example 1. A thermally reversible cross-linked polymer, comprising: a polysiloxane backbone comprising pendant groups, each pendant group comprising a diene moiety connected to the polysiloxane backbone through a urea or urethane linkage; a crosslinker comprising two or more dienophile moieties; and reversible crosslinks formed between the first and second Diels-Alder reactive moieties (e.g. through Diels-Alder cycloaddition), wherein the reversible crosslinks form at a first temperature range and break (e.g., via retro-Diels-Alder reaction) at a second temperature range higher than the first temperature range.

[0274] Example 2. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the polysiloxane backbone comprises polydimethylsiloxane (PDMS).

[0275] Example 3. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the first Diels-Alder reactive moieties comprise diene moieties and the second Diels-Alder reactive moieties comprise dienophile moieties. In some embodiments, the diene moieties comprise furan groups and the dienophile moieties comprise maleimide groups.

[0276] Example 4. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the pendant group comprises a furfuryl group connected to the polysiloxane backbone through a urea linkage formed by reaction of an amine-functionalized polysiloxane with furfuryl isocyanate.

[0277] Example 5. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the crosslinker comprises a bismaleimide.

[0278] Example 6. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the first temperature range is from approximatelyInternational Patent Application Docket No. 009062.8583.WO00 50°C to approximately 80°C and the second temperature range is from approximately 90°C to approximately 150°C.

[0279] Example 7. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the reversible crosslinks comprise endo and exo diastereomeric adducts; and the exo diastereomeric adducts constitute at least approximately 50% of total adducts.

[0280] Example 8. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the thermally reversible cross-linked polymer is optically transparent with an average transmittance of at least approximately 85% across a wavelength range of 400-1100 nm when disposed between two glass substrates.

[0281] Example 9. A photovoltaic module comprising: a first substrate; a second substrate; an encapsulant material disposed between the first substrate and the second substrate; and at least one layer of a thermally reversible cross-linked polymer disposed at one or more interfaces within the photovoltaic module, wherein the at least one layer of the thermally reversible cross-linked polymer is configured to transition from a crosslinked state to a de-cross-linked state upon heating to a de-crosslinking temperature, thereby facilitating separation of components of the photovoltaic module.

[0282] Example 10. The photovoltaic module of any one or more examples disclosed herein, wherein at least one of the first substrate or the second substrate comprises glass.

[0283] Example 11. The photovoltaic module of any one or more examples disclosed herein, wherein the encapsulant material comprises ethylene vinyl acetate (EVA), polyolefin elastomer (POE), or polyurethane.

[0284] Example 12. The photovoltaic module of any one or more examples disclosed herein, wherein the layer of the thermally reversible cross-linked polymer has a refractive index that substantially matches a refractive index of the first substrate or the second substrate.

[0285] Example 13. The photovoltaic module of any one or more examples disclosed herein, wherein the thermally reversible cross-linked polymer comprises a polysiloxane backbone with reversible Diels-Alder crosslinks. In some embodiments, the photovoltaic module of any one or more examples disclosed herein, wherein the thermally reversibleInternational Patent Application Docket No. 009062.8583.WO00 cross-linked polymer comprises furan-functionalized polydimethylsiloxane cross-linked with a bismaleimide.

[0286] Example 14. The photovoltaic module of any one or more examples disclosed herein, wherein the layer of the thermally reversible cross-linked polymer exhibits a shear strength of at least approximately 100 kPa in the cross-linked state and a shear strength of no more than approximately 0.05 kPa in the de-cross-linked state.

[0287] Example 15. The photovoltaic module of any one or more examples disclosed herein, further comprising at least one photovoltaic cell disposed between the first substrate and the second substrate.

[0288] Example 16. The photovoltaic module of any one or more examples disclosed herein, wherein the layer of thermally reversible cross-linked polymer is disposed between the encapsulant material and the photovoltaic cell to facilitate recovery of the photovoltaic cell.

[0289] Example 17. A method of recycling a photovoltaic module, comprising: providing a photovoltaic module comprising a first substrate, a second substrate, an encapsulant material disposed between the first substrate and the second substrate, and a layer of a thermally reversible cross-linked polymer disposed between the encapsulant material and at least one of the first substrate or the second substrate; heating the photovoltaic module to a de-crosslinking temperature sufficient to break reversible crosslinks in the thermally reversible cross-linked polymer; and separating at least one of the first substrate or the second substrate from the encapsulant material. In some embodiments, the polymer comprises reversible Diels-Alder crosslinks. In some embodiments, heating comprises heating the photovoltaic module to a de-crosslinking temperature sufficient to break the reversible Diels-Alder crosslinks in the thermally reversible cross-linked polymer via retro-Diels-Alder reaction.

[0290] Example 18. The method of any one or more examples disclosed herein, wherein the de-crosslinking temperature is from approximately 90°C to approximately 150°C.

[0291] Example 19. The method of any one or more examples disclosed herein, wherein separating comprises manually separating the first substrate or the second substrate from the encapsulant material.International Patent Application Docket No. 009062.8583.WO00

[0292] Example 20. The method of any one or more examples disclosed herein, further comprising, after separating, re-combining the first substrate or the second substrate with the encapsulant material and heating to a crosslinking temperature to reform the reversible Diels-Alder crosslinks.

[0293] Example 21. The method of any one or more examples disclosed herein, wherein the thermally reversible cross-linked polymer comprises a polysiloxane backbone comprising pendant furan moieties connected through urea linkages, crosslinked with a bismaleimide through Diels-Alder cycloaddition, and wherein the layer of the thermally reversible cross-linked polymer is optically transparent.

[0294] Example 22. The method of any one or more examples disclosed herein, wherein the separating is performed free of chemical intervention or aggressive chemical degradation, such that the separated components are recovered with substantially clean surfaces having minimal adhesive residue.

[0295] Example 23. A method of preparing a thermally reversible cross-linked polymer, comprising: providing a polydimethylsiloxane (PDMS) comprising first Diels-Alder reactive groups; providing a crosslinker comprising second Diels-Alder reactive groups complementary to the first Diels-Alder reactive groups; combining the PDMS and the crosslinker; and heating the combination at a first temperature to form reversible crosslinks between the first and second Diels-Alder reactive groups through Diels-Alder cycloaddition, wherein the reversible crosslinks break when heated at a second temperature different from the first temperature.

[0296] Example 24. The method of any one or more examples disclosed herein, wherein providing the PDMS comprising first Diels-Alder reactive groups comprises: performing a metal-free addition reaction between an amine-functionalized PDMS and an isocyanate-functionalized compound comprising a Diels-Alder reactive group to form urea linkages.

[0297] Example 25. The method of any one or more examples disclosed herein, wherein: the first Diels-Alder reactive groups comprise diene groups; the second Diels-Alder reactive groups comprise dienophile groups; and the crosslinker comprises two or more of the dienophile groups.International Patent Application Docket No. 009062.8583.WO00

[0298] Example 26. A thermally reversible cross-linked polymer obtained by a process comprising: providing a polydimethylsiloxane (PDMS) comprising first Diels-Alder reactive groups; providing a crosslinker comprising second Diels-Alder reactive groups complementary to the first Diels-Alder reactive groups; combining the PDMS and the crosslinker; and heating the combination at a first temperature to form reversible crosslinks between the first and second Diels-Alder reactive groups through Diels-Alder cycloaddition, wherein the reversible crosslinks break when heated at a second temperature different from the first temperature.

[0299] Example 27. A thermally reversible cross-linked polymer, comprising: a polydimethylsiloxane (PDMS) comprising first Diels-Alder reactive groups; a crosslinker comprising second Diels-Alder reactive groups complementary to the first Diels-Alder reactive groups; and reversible crosslinks formed between the first and second Diels-Alder reactive groups through Diels-Alder cycloaddition, wherein the reversible crosslinks form at a first temperature range and break at a second temperature that is different from the first temperature range.

[0300] Example 28. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the thermally reversible cross-linked polymer is optically transparent.

[0301] Example 29. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein: the first Diels-Alder reactive groups comprise diene groups; the second Diels-Alder reactive groups comprise dienophile groups; and the crosslinker comprises two or more of the dienophile groups.

[0302] Example 30. A thermally reversible cross-linked polymer, comprising: a polysiloxane backbone comprising pendant groups; and reversible covalent crosslinks formed between the pendant groups and a crosslinker, wherein the reversible covalent crosslinks are configured to form at a first temperature range and break at a second temperature range higher than the first temperature range, and wherein the reversible covalent crosslinks comprise one or more of: Diels-Alder adducts, disulfide bonds, dioxaborolane linkages, or vinylogous urethane linkages.International Patent Application Docket No. 009062.8583.WO00

[0303] Example 31. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the polysiloxane backbone comprises polydimethylsiloxane (PDMS).

[0304] Example 32. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the reversible covalent crosslinks comprise Diels-Alder adducts.

[0305] Example 33. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the pendant groups comprise diene moieties and the crosslinker comprises two or more dienophile moieties.

[0306] Example 34. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the diene moieties comprise furan groups and the dienophile moieties comprise maleimide groups.

[0307] Example 35. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the reversible covalent crosslinks comprise disulfide bonds.

[0308] Example 36. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the pendant groups are connected to the polysiloxane backbone through urea or urethane linkages.

[0309] Example 37. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the first temperature range is from approximately 50°C to approximately 80°C and the second temperature range is from approximately 90°C to approximately 150°C.

[0310] Example 38. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the thermally reversible cross-linked polymer is optically transparent with an average transmittance of at least approximately 85% across a wavelength range of 400-1100 nm when disposed between two glass substrates.

[0311] Example 39. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the reversible covalent crosslinks comprise dioxaborolane linkages.International Patent Application Docket No. 009062.8583.WO00

[0312] Example 40. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the reversible covalent crosslinks comprise vinylogous urethane linkages.

[0313] Example 41. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the reversible covalent crosslinks comprise two or more different types of reversible covalent crosslinks.

[0314] Example 42. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the reversible covalent crosslinks are configured to break by one or more of: a retro-Diels-Alder reaction, reduction, thiol— di sulf ide exchange, metathesis exchange, or transamination.

[0315] Example 43. The thermally reversible cross-linked polymer of any one or more examples disclosed herein, wherein the pendant groups comprise diene or dienophile moieties connected to the polysiloxane backbone through urea or urethane linkages.

[0316] Example 44. A photovoltaic (PV) module comprising: a first substrate; a second substrate; at least one photovoltaic cell positioned between the first substrate and the second substrate; an encapsulant material surrounding the at least one photovoltaic cell; and at least one layer of a thermally reversible cross-linked polymer as disclosed herein. The at least one layer of the thermally reversible cross-linked polymer may be positioned between, e.g., the encapsulant material and at least one of the first or second substrate.

[0317] Example 45. The PV module of any one or more examples disclosed herein, wherein the thermally reversible cross-linked polymer facilitates separation of the encapsulant material and at least one of the first or second substrate when heated to break reversible crosslinks within the polymer.

[0318] Example 46. The PV module of any one or more examples disclosed herein, wherein the first substrate is transparent to allow light transmission.

[0319] Example 47. The PV module of any one or more examples disclosed herein, wherein at least one of the first substrate or the second substrate comprises a glass sheet.

[0320] Example 48. The PV module of any one or more examples disclosed herein, wherein the thermally reversible cross-linked polymer is optically transparent.

[0321] Example 49. A method of making a photovoltaic (PV) module, comprising: providing a first substrate; providing a second substrate; positioning at least oneInternational Patent Application Docket No. 009062.8583.WO00 photovoltaic cell between the first substrate and the back substrate; surrounding the at least one photovoltaic cell with an encapsulant material; and providing a layer of a thermally reversible cross-linked polymer between the encapsulant material and at least one of the first or second substrate.

[0322] Example 50. A method of preparing a thermally reversible cross-linked polymer as shown and described herein.

[0323] Example 51. A thermally reversible cross-linked polymer as shown and described herein.

[0324] Example 52. A photovoltaic (PV) module as shown and described herein.

[0325] Example 53. A method of making a photovoltaic (PV) module as shown and described herein.

[0326] The use of reversibly-crosslinked polymers presents a transformative approach to facilitate the recyclability and sustainability of PV modules. By working alongside commercial encapsulants like EVA, the ReCLIP formulation combines reversible mechanical adhesion and integrity with optical and mechanical compatibility. Its ability to enable clean delamination may serve as a key enabler of circular PV systems.

[0327] The polymer (ReCLIP) utilizes reversible crosslinking chemistry, enabling controlled decrosslinking. This feature makes it unique compared to traditional encapsulants like EVA, polyurethane, or POE, which are permanently crosslinked and difficult to separate at the end of life. The technology allows PV modules to be easily disassembled without excessive mechanical force or chemical treatments. This reduces energy and operational costs compared to existing methods, which typically involve aggressive thermal or chemical processes to separate components.

[0328] The polymer synthesis utilizes an isocyanate addition reaction between amine-functionalized PDMS and isocyanate-functionalized compounds to form urea linkages. The reaction proceeds without requiring precious metal catalysts (e.g., platinum or gold), which are commonly needed in other PDMS-type reactions. The metal-free synthesis achieves (approximately) 100% atom economy with no side products generated or catalyst poisoning. The synthesis can be performed using environmentally friendly solvents, and both solvents and triethylamine can be recovered for flow reaction andInternational Patent Application Docket No. 009062.8583.WO00 mass production in a single system. This approach enables high-throughput manufacturing, while simplifying the synthesis process and reducing both costs and material waste.

[0329] ReCLIP is designed to work alongside standard encapsulants such as EVA, polyurethane, or POE. This enables seamless integration into existing module manufacturing processes without requiring major changes to equipment or materials. By enabling clean separation of glass, cells, and encapsulants, embodiments of the technology allow for high-purity recovery of valuable materials like silicon and metals, which is beneficial for cost-effective and scalable PV recycling.

[0330] Beyond recycling, the polymer may allow for refurbishing and repowering PV modules by facilitating easy repairs or upgrades, which current encapsulants cannot support due to their permanent bonding. The process significantly reduces the environmental footprint of PV module recycling by eliminating harsh chemical treatments and high-temperature processes, contributing to a circular economy in the solar industry.

[0331] ReCLIP has been successfully synthesized, processed, and integrated into small-scale photovoltaic laminate prototypes. Prototypes include Glass / ReCLIP-EVA-ReCLIP / Glass and Glass / ReCLIP / Glass configurations, fabricated using industrystandard lamination processes. Comprehensive experimental data supports the technology, including peel tests, lap shear tests, UV-Vis spectroscopy, and thermal reversibility studies.

[0332] ReCLIP stands out due to its practical operating conditions, compatibility with existing materials, and ability to balance high adhesive strength during operation with reversible delamination at moderate temperatures. Unlike existing approaches, it does not require aggressive thermal or chemical processes, making it more sustainable, cost-effective, and scalable for industrial adoption.

[0333] The technology enables systematic variation of multiple parameters. Below are exemplary variations that may be employed alone or in combination. The PDMS molecular weight and amine content can be adjusted to control crosslinking density. The amine groups can be substituted with hydroxyls to form urethane instead of urea motifs in the pendant group. The crosslinker architecture can range from two-arm (bismaleimide) to multi-arm (tri-, tetra-, or n-arm) maleimide structures. The linker between maleimideInternational Patent Application Docket No. 009062.8583.WO00 groups can be modified from aromatic to aliphatic structures with variable molecular weight. The linker can incorporate chemical sensory molecules for specific detection capabilities.

[0334] The material has ample uses. As recyclable adhesives in photovoltaic (PV) modules, the material facilitates module recycling through component separation. In medical technologies, the material's bio-compatibility and bio-orthogonal reaction systems make it suitable for implants, adhesive bandages, scaffolds, and molds. The material can also function as degradable, emergency coatings or sealants to stop crack propagation on optically transparent surfaces such as glass or plastic. The incorporation of chemical sensory molecules enables additional functionalities such as damage detection in industrial applications or anti-bacterial and antifungal properties in biological applications.

[0335] While this patent document contains many specifics, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this patent document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0336] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments.International Patent Application Docket No. 009062.8583.WQ00

[0337] Only a few implementations and examples are described and other implementations, enhancements and variations can be made based on what is described and illustrated in this patent document.

Claims

International Patent Application Docket No. 009062.8583.WO00 CLAIMSWhat is claimed is:

1. A thermally reversible cross-linked polymer, comprising:a polysiloxane backbone comprising pendant groups, each pendant group comprising a first Diels-Alder reactive moiety connected to the polysiloxane backbone through a urea or urethane linkage;a crosslinker comprising two or more second Diels-Alder reactive moieties complementary to the first Diels-Alder reactive moieties; and reversible crosslinks formed between the first and second Diels-Alder reactive moieties, wherein the reversible crosslinks form at a first temperature range and break at a second temperature range higher than the first temperature range.

2. The thermally reversible cross-linked polymer of claim 1 , wherein the polysiloxane backbone comprises polydimethylsiloxane (PDMS).

3. The thermally reversible cross-linked polymer of claim 1 , wherein the first Diels-Alder reactive moieties comprise diene moieties and the second Diels-Alder reactive moieties comprise dienophile moieties.

4. The thermally reversible cross-linked polymer of claim 3, wherein the diene moieties comprise furan groups and the dienophile moieties comprise maleimide groups.

5. The thermally reversible cross-linked polymer of claim 4, wherein the pendant group comprises a furfuryl group connected to the polysiloxane backbone through a urea linkage formed by reaction of an amine-functionalized polysiloxane with furfuryl isocyanate.International Patent Application Docket No. 009062.8583.WO00 6. The thermally reversible cross-linked polymer of claim 4, wherein the crosslinker comprises a bismaleimide.

7. The thermally reversible cross-linked polymer of claim 1 , wherein the first temperature range is from approximately 50°C to approximately 80°C and the second temperature range is from approximately 90°C to approximately 150°C.

8. The thermally reversible cross-linked polymer of claim 1 , wherein:the reversible crosslinks comprise endo and exo diastereomeric adducts; and the exo diastereomeric adducts constitute at least approximately 50% of total adducts.

9. The thermally reversible cross-linked polymer of claim 1 , wherein the thermally reversible cross-linked polymer is optically transparent with an average transmittance of at least approximately 85% across a wavelength range of 400-1100 nm when disposed between two glass substrates.

10. A photovoltaic module comprising:a first substrate;a second substrate;an encapsulant material disposed between the first substrate and the second substrate; andat least one layer of a thermally reversible cross-linked polymer disposed at one or more interfaces within the photovoltaic module, wherein the at least one layer of the thermally reversible cross-linked polymer is configured to transition from a cross-linked state to a de-cross-linked state upon heating to a de-crosslinking temperature, thereby facilitating separation of components of the photovoltaic module.

11. The photovoltaic module of claim 10, wherein at least one of the first substrate or the second substrate comprises glass.International Patent Application Docket No. 009062.8583.WO0012. The photovoltaic module of claim 10, wherein the encapsulant material comprises ethylene vinyl acetate (EVA), polyolefin elastomer (POE), or polyurethane.

13. The photovoltaic module of claim 10, wherein the layer of the thermally reversible cross-linked polymer has a refractive index that substantially matches a refractive index of the first substrate or the second substrate.

14. The photovoltaic module of claim 10, wherein the thermally reversible crosslinked polymer comprises a polysiloxane backbone with reversible Diels-Alder crosslinks.

15. The photovoltaic module of claim 10, wherein the layer of the thermally reversible cross-linked polymer exhibits a shear strength of at least approximately 100 kPa in the cross-linked state and a shear strength of no more than approximately 0.05 kPa in the de-cross-linked state.

16. The photovoltaic module of claim 10, further comprising at least one photovoltaic cell disposed between the first substrate and the second substrate.

17. The photovoltaic module of claim 16, wherein the layer of thermally reversible cross-linked polymer is disposed between the encapsulant material and the photovoltaic cell to facilitate recovery of the photovoltaic cell.

18. A method of recycling a photovoltaic module, comprising:providing a photovoltaic module comprising a first substrate, a second substrate, an encapsulant material disposed between the first substrate and the second substrate, and a layer of a thermally reversible cross-linked polymer disposed between the encapsulant material and at least one of the first substrate or the second substrate;International Patent Application Docket No. 009062.8583.WO00 heating the photovoltaic module to a de-crosslinking temperature sufficient to break reversible crosslinks in the thermally reversible cross-linked polymer; andseparating at least one of the first substrate or the second substrate from the encapsulant material.

19. The method of claim 18, wherein the de-crosslinking temperature is from approximately 90°C to approximately 150°C.

20. The method of claim 18, wherein the polymer comprises reversible Diels-Alder crosslinks.

21. The method of claim 18, wherein separating comprises manually separating the first substrate or the second substrate from the encapsulant material.

22. The method of claim 18, comprising, after separating, re-combining the first substrate or the second substrate with the encapsulant material and heating to a crosslinking temperature to re-form the reversible crosslinks.

23. The method of claim 18, wherein the thermally reversible cross-linked polymer comprises a polysiloxane backbone comprising pendant furan moieties connected through urea linkages, cross-linked with a bismaleimide through Diels-Alder cycloaddition, and wherein the layer of the thermally reversible cross-linked polymer is optically transparent.

24. The method of claim 18, wherein the separating is performed free of chemical intervention or aggressive chemical degradation, such that the separated components are recovered with substantially clean surfaces having minimal adhesive residue.

Images