Flexible organic solar cell containing cross-linking agent with adjustable cross-linking characteristic and preparation method thereof

Abstract

The invention belongs to the technical field of flexible solar cells, and relates to a flexible organic solar cell containing a cross-linking agent with adjustable cross-linking characteristics and a preparation method of the flexible organic solar cell. The invention discloses a flexible organic solar cell containing a cross-linking agent with adjustable cross-linking characteristics. The flexible organic solar cell sequentially comprises a substrate, a positive electrode, a hole transport layer, an active layer, an electron transport layer and a metal electrode from bottom to top, the active layer comprises 1 to 10 weight percent of lipoic acid-polyethylene glycol-carboxyl; the active layer further comprises a donor material and an acceptor material, the donor material is selected from PM6, D18, PTQ10 and / or PCE10, and the acceptor material is selected from Y6, N3, Y6-BO, BTP-eC9 and / or L8-BO. Lipoic acid-polyethylene glycol-carboxyl is added into the active layer to serve as a cross-linking agent, the cross-linking agent can form an adjustable cross-linked network in situ in the preparation process, and the mechanical strength, toughness and durability of the film can be remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of flexible solar cell technology, and relates to a flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties and its preparation method. Background Technology

[0002] Organic solar cells (OSCs) have attracted widespread attention and become a research hotspot due to their lightweight, low cost, flexibility, and semi-transparency, and their potential applications in future multifunctional self-powered greenhouses and building-integrated photovoltaics (BIPV). Flexible organic solar cells (f-OSCs) are the best choice for wearable / portable power applications due to their lightweight and flexibility. However, the photoelectric conversion efficiency (PCE) of f-OSCs still lags significantly behind that of rigid devices. In terms of mechanical properties, non-fullerene small molecule acceptors (NF-SMAs) with rigid frameworks tend to form discontinuous crystals and sharp boundaries in blend films, leading to film embrittlement and poor mechanical ductility of the functional layers. To date, many strategies have been proposed, including material design units, multi-component strategies, and interface engineering, and applied to adjust the PCE and mechanical stability of f-OSCs. However, these flexible devices still have limitations in terms of photovoltaic performance and bending cycle performance. Furthermore, under continuous bending or stretching cycles, irreversible microcracks in the functional layers and delamination of adjacent layers significantly shorten the device's lifespan. Therefore, more efforts are needed to synergistically improve the PCE and mechanical stability of f-OSCs. In recent years, multi-component blending active layer strategies have attracted much attention due to their great potential in optimizing the phase separation morphology of active layer films in three-dimensional space and improving carrier lifetime. However, no work has yet emerged that can improve the mechanical properties, toughness, and durability of multi-component flexible organic solar cells by introducing crosslinking agents with adjustable crosslinking properties to form an in-situ crosslinking network, passivating defects in multi-component blended films, and simultaneously improving photovoltaic performance.

[0003] However, the crosslinking agents currently used in the market and in this research field have significant limitations and cannot be effectively applied to flexible organic solar cell systems. Specifically, existing crosslinking agents typically have high rigidity of molecular structure or high crosslinking density. This not only restricts the freedom of movement of molecular chain segments within the blended active layer, leading to brittle fracture and irreversible microcracks under strain conditions, but also makes it difficult to achieve good intermolecular compatibility with the blended active layer. Furthermore, traditional crosslinking agents often suffer from uncontrollable crosslinking reactions, easily causing over- or under-crosslinking, which severely affects the precise control of the three-dimensional network structure in the film, resulting in hindered carrier migration, reduced photoelectric conversion efficiency, and an inability to achieve the desired balance of mechanical toughness. Therefore, existing crosslinking agents cannot meet the comprehensive requirements of both efficiently improving mechanical properties and significantly optimizing photovoltaic performance in the active layer of multi-component flexible organic solar cells. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in the prior art by proposing an active layer made of donor material, acceptor material, and crosslinking agent, which is then applied to flexible organic solar cells and exhibits excellent mechanical and photovoltaic properties.

[0005] One objective of this invention is achieved through the following technical solution: A flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties, the flexible organic solar cell comprising, from bottom to top: a substrate, a positive electrode, a hole transport layer, an active layer, an electron transport layer, and a metal electrode; The active layer includes 1-10 wt% lipoic acid-polyethylene glycol-carboxyl group. The active layer further includes a donor material and an acceptor material, wherein the donor material is selected from PM6, D18, PTQ10 and / or PCE10, and the acceptor material is selected from Y6, N3, Y6-BO, BTP-eC9 and / or L8-BO.

[0006] Preferably, the groups of the Lipoic acid-PEG-acid include: cyclic disulfide bonds, -NH-CO-, -OCH2CH2- and -COOH.

[0007] Preferably, the Lipoic acid-PEG-acid is prepared by reacting lipoic acid-NHS ester and NH2-PEG-COOH.

[0008] Preferably, the structural formula of the Lipoic acid-PEG-acid is shown in formula (1). Equation (1), Where n is 2 to 30.

[0009] Further preferred, the 4~21.

[0010] Preferably, the mass ratio of the donor material to the acceptor material is 1:(0.7~1.6).

[0011] Further preferably, the mass ratio of the donor material to the acceptor material is 1:1.2.

[0012] Preferably, when the donor material is PM6 and D18, the acceptor material is L8-BO and BTP-eC9.

[0013] Further preferred, the mass ratio of PM6, D18, L8-BO, and BTP-eC9 is (0.6~1.2):(0~0.4):(0~1.2):(0.1~1.6).

[0014] Further preferred, the mass ratio of PM6, D18, L8-BO, and BTP-eC9 is (0.7~1):(0.05~0.2):(0.9~1.2):(0.1~0.3).

[0015] More preferably, the mass ratio of PM6, D18, L8-BO, and BTP-eC9 is 0.9:0.1:1:0.2.

[0016] Preferably, the active layer is prepared by mixing a donor material, an acceptor material, Lipoic acid-PEG-acid, and an organic solvent, heating and stirring, and then spin-coating and annealing.

[0017] Preferably, the substrate is a flexible substrate selected from polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyimide (PI), cyclic olefin polymer (COP), or ultrathin flexible glass (UTG).

[0018] Preferably, the thickness of the substrate is 0.1~0.3 mm.

[0019] Preferably, the anode is selected from indium tin oxide (ITO), indium tin fluoride (FTO), or aluminum-doped zinc oxide (AZO).

[0020] Preferably, the thickness of the anode is 50~90 nm.

[0021] Preferably, the hole transport layer is selected from [2-(9H-carbazole-9-yl)ethyl]phosphonic acid (2PACz), [4-(9H-carbazole-9-yl)butyl]phosphonic acid (4PACz), [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (MeO-2PACz), [4-(7H-dibenzo[c,g]carbazole-7-yl)butyl]phosphonic acid (4PADCB), [4-(3,11-dimethoxy-7H-dibenzo[c,g]carbazole-7-yl]... [2,7-Dimethoxy-9H-carbazole-9-yl)methyl]phosphonic acid (MeO-4PADBC), [2,7-dimethoxy-9H-carbazole-9-yl)methyl]phosphonic acid (DC-PA), [2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanovinyl]phosphonic acid (MPA-CPA), [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz) or [2-(3,6-dimethoxy-9H-carbazole-9-yl)butyl]phosphonic acid (MeO-4PACz).

[0022] Preferably, the thickness of the hole transport layer is 20~60 nm.

[0023] Preferably, the thickness of the active layer is 80~200 nm.

[0024] Preferably, the electron transport layer is selected from PDINN, PDINO, or PFN-Br.

[0025] Preferably, the thickness of the electron transport layer is 10~30 nm.

[0026] Preferably, the metal electrode is selected from Ag, Al, Au or Cu.

[0027] Preferably, the thickness of the metal electrode is 100~150 nm.

[0028] Preferably, the thickness of the flexible organic solar cell containing the crosslinking agent with adjustable crosslinking properties is 50~500μm.

[0029] The second objective of this invention is achieved through the following technical solution: A method for preparing a flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties, comprising: (1) pretreatment of a flexible substrate; (2) Attach a positive electrode to the surface of a flexible substrate and perform surface treatment; (3) A hole transport layer is formed on the surface of the anode, wherein the method for forming the hole transport layer includes: spin-coating a hole transport layer solution onto the surface of the anode and then annealing it; (4) An active layer is formed on the surface of the hole transport layer. The method for preparing the active layer includes: mixing a donor material, an acceptor material, Lipoicacid-PEG-acid and an organic solvent to obtain an active layer solution, and then spin-coating the active layer solution onto the surface of the hole transport layer and annealing it. (5) An electron transport layer is formed on the surface of the active layer, wherein the method for forming the electron transport layer includes spin-coating an electron transport layer solution onto the surface of the active layer; (6) Fabricate metal electrodes on the surface of the electron transport layer.

[0030] Preferably, the pretreatment of the substrate in (1) includes one or more of the following: cleaning agent cleaning, acetone cleaning, isopropanol cleaning, deionized water washing, ultrasonic treatment, plasma treatment, and surface activation.

[0031] Preferably, the anode in (2) is fabricated by vapor deposition, vacuum evaporation, electron beam evaporation deposition, photoresist etching, or laser direct writing.

[0032] Preferably, the surface treatment in (2) includes cleaning and plasma surface treatment, and the plasma surface treatment time is 1~20 min.

[0033] More preferably, the cleaning includes one or more of the following: cleaning agent cleaning, acetone cleaning, isopropanol cleaning, and deionized water washing.

[0034] Preferably, the hole transport layer solution in (3) is a 4PADCB solution with a concentration of 0.1~5 mg / m.

[0035] Preferably, in the spin coating process of (3), the spin coating speed is 3000~8000 rpm and the spin coating time is 30~45s; the annealing temperature is 80~100℃ and the time is 5~10min.

[0036] Preferably, the preparation method of the active layer solution in (4) includes: mixing donor material, acceptor material, Lipoic acid-PEG-acid and organic solvent in a mass ratio of 1:1.2:0.4, heating and stirring to obtain an active layer solution with a concentration of 10~30mg / mL.

[0037] Preferably, in the spin coating process of (4), the spin coating speed is 3000~8000 rpm and the spin coating time is 30~45s; the annealing temperature is 90~120℃ and the time is 1~20min.

[0038] Preferably, the electron transport layer solution in (5) is a PDINN solution, which is prepared by dissolving PDINN in methanol solution, and the concentration of the PDINN solution is 0.1~5 mg / mL.

[0039] Preferably, in the spin coating process described in (5), the spin coating speed is 1000~8000 rpm and the spin coating time is 30~45s.

[0040] Preferably, the metal electrode in (6) is selected from Ag, Al, Au or Cu.

[0041] Preferably, the metal electrode in (6) is fabricated by vapor deposition, vacuum evaporation, electron beam evaporation deposition, photoresist etching, or laser direct writing. Compared with the prior art, the present invention has the following beneficial effects: 1. In this invention, Lipoic acid-PEG-acid is added to the active layer as a crosslinking agent. This crosslinking agent contains dynamic covalent bonds, hydrogen bonds, and functional groups with high reactivity and structural flexibility. During the preparation process, the crosslinking agent can form an adjustable crosslinking network in situ. The formation of the crosslinking network promotes the establishment of a tight and stable ordered structure in the active layer film, which can significantly improve the mechanical strength, toughness and durability of the film. At the same time, the crosslinking network "freezes" the donor-acceptor phase separation structure at an ideal scale, and the donor and acceptor are "tightly bound" within the crosslinking network.

[0042] 2. In the active layer material of the present invention, the donor material and the acceptor material optimize the phase separation structure through interaction, and the spectral overlap enhances the absorption in the 500~650 nm range, which greatly improves the photovoltaic performance.

[0043] 3. The present invention selects 4PADCB as the hole transport layer, introducing two benzene rings into the carbazole group of commercial 4PACz, which improves the film formation and charge transport / collection of SAM on flexible substrates. At the same time, as an interface layer, it promotes the formation and stability of the cross-linked network of the active layer blend film, and the ordered molecular arrangement enhances the extraction and transport of interfacial charges.

[0044] 4. The active layer of this invention is located in the middle of the flexible organic solar cell. It generates excitons by absorbing photons and forms charge carriers inside, providing a basis for charge separation and transport. By introducing a crosslinking agent into the active layer to form a crosslinked network structure, this invention not only significantly improves photovoltaic conversion efficiency but also enhances the mechanical strength of the material, thereby optimizing the overall performance of the flexible organic solar cell.

[0045] 5. The flexible organic solar cell of the present invention has good bending cycle performance, mechanical strength and toughness, and maintains excellent performance in a variety of working environments. Attached Figure Description

[0046] Figure 1 This is a flowchart illustrating the fabrication process of the flexible organic solar cell in this invention.

[0047] Figure 2 This is a schematic diagram of the layered structure of the flexible organic solar cell in Embodiment 1 of the present invention.

[0048] Figure 3 This is a schematic diagram of the crosslinking reaction of the crosslinking agent described in this invention.

[0049] Figure 4 This is a schematic diagram of the crosslinking network formed by the crosslinking agent described in Embodiment 1 of the present invention.

[0050] Figure 5 These are the tensile stress-strain curves of the flexible organic solar cell units in Embodiments 1 and 5 of the present invention.

[0051] Figure 6 These are JV curves of the flexible organic solar cell units in Embodiments 1, 5, Comparative Example 1, and Comparative Example 2 of the present invention. Detailed Implementation

[0052] The technical solution of the present invention will be further described and illustrated below through specific embodiments. It should be understood that the specific embodiments described herein are only for the purpose of helping to understand the present invention and are not intended to limit the present invention.

[0053] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used in the art, and the methods used in the embodiments are all conventional methods in the art.

[0054] In this article, Lipoic acid-PEG-acid was custom-made and purchased externally; The structural formula of the Lipoic acid-PEG-acid is shown in formula (1). Equation (1), Where n is 12.

[0055] In this paper, the molecular weight of PEG in Lipoic acid-PEG-acid is 200~1000, which can achieve the effects described in this invention.

[0056] In this paper, the crosslinking agent Lipoic acid-PEG-acid contains multiple groups, but not all raw materials containing all of these groups can achieve the effects of this invention.

[0057] In this article, the fabrication process of flexible organic solar cells is shown in the following flowchart. Figure 1 As shown, according to the battery structure, the substrate, anode, hole transport layer, active layer, electron transport layer and metal electrode are prepared sequentially from bottom to top.

[0058] In this paper, the flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties includes, from bottom to top: a substrate, an anode, a hole transport layer, an active layer, an electron transport layer, and a metal electrode. The substrate is a flexible substrate selected from polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyimide (PI), cyclic olefin polymer (COP), or ultrathin flexible glass (UTG); the thickness of the substrate is 0.1~0.3 mm. The anode is selected from indium tin oxide (ITO), indium tin fluoride (FTO), or aluminum-doped zinc oxide (AZO); the thickness of the anode is 50-90 nm.

[0059] The hole transport layer is selected from 2PACz, 4PACz, MeO-2PACz, 4PADCB, MeO-4PADBC, DC-PA, MPA-CPA, Me-4PACz or MeO-4PACz; the thickness of the hole transport layer is 20~60 nm. The active layer comprises a donor material, an acceptor material, and Lipoic acid-PEG-acid in a mass ratio of 1:1.2:(0.1~1); the donor material is selected from PM6, D18, PTQ10, and / or PCE10; the acceptor material is selected from Y6, N3, Y6-BO, BTP-eC9, and / or L8-BO; the thickness of the active layer is 80~200 nm. The electron transport layer is selected from PDINN or PFN-Br; the thickness of the electron transport layer is 10~30 nm. The metal electrode is selected from Ag, Al, Au or Cu; the thickness of the metal electrode is 100~150 nm.

[0060] In this paper, the structure of the SAM hole transport layer material 4PADCB is as follows (2). Equation (2).

[0061] In this paper, the tensile stress-strain curves were determined by floating thin film (FOW) tensile tests to obtain the crack initiation strain (COSFOW) based on the blend film.

[0062] Example 1 The structure of the flexible organic solar cell in this embodiment, which contains a crosslinking agent with adjustable crosslinking properties, is as follows: Figure 2 As shown: PEN / ITO / 4PADCB / PM6:D18-CL:L8-BO:BTP-eC9 (4wt% Lipoic acid-PEG-acid) / PDINN / Ag, from bottom to top, includes: PEN substrate (0.125mm), ITO anode (60nm), hole transport layer 4PADCB (35nm), active layer (150nm), electron transport layer PDINN (20nm) and metal electrode layer Ag (150nm).

[0063] Methods for preparing flexible organic solar cells containing crosslinking agents with adjustable crosslinking properties include: (1) Polyethylene naphthalate (PEN) was selected as the flexible substrate and pretreated: the flexible substrate was ultrasonically cleaned with cleaning agent and deionized water for 20 minutes in sequence. (2) An ITO anode was deposited on the pretreated flexible substrate by electron beam deposition and then post-treated: it was ultrasonically cleaned with deionized water, acetone and isopropanol for 20 minutes in sequence, dried and then subjected to plasma surface treatment with a power of 50W for 5 minutes.

[0064] (3) A hole transport layer is prepared on the surface of the anode. The preparation method of the hole transport layer includes: mixing 4PADCB with methanol to prepare a 4PADCB solution with a concentration of 0.5 mg / ml; spin-coating the 4PADCB solution onto the surface of the anode at a spin speed of 5000 rpm for 40 s, and then annealing at 120°C for 40 min. (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6, D18-CL, L8-BO, and BTP-eC9 (mass ratio of 0.9:0.1:0.2:1) in chloroform, adding 4wt% of Lipoic acid-PEG-acid, heating and stirring at 55°C for 3h to obtain an active layer solution with a concentration of 16mg / ml, spin-coating the active layer solution onto the surface of the hole transport layer at a spin speed of 3500rpm for 30s, and then annealing at 100°C for 10min. A schematic diagram of the crosslinking reaction of the crosslinking agent Lipoic acid-PEG-acid, and a schematic diagram of the crosslinking network formed by the crosslinking agent Lipoic acid-PEG-acid are shown below. Figure 3 , 4 As shown.

[0065] The crosslinking agent cures at low temperatures. Lipoic acid-PEG-acid first forms linear poly(Lipoic acid-PEG-acid) through ring-opening polymerization of disulfide bonds. Dynamic bonds, through reversible bond cleavage and reformation, promote stress dissipation in the stretched polymer film, which is beneficial for forming an ideal blend film morphology with high ductility. Furthermore, the functional groups in the crosslinking agent, after annealing, can form a tunable crosslinking network in situ, which helps to finely control the molecular packing morphology and phase separation structure, making the film exhibit stronger resistance to external stress.

[0066] (5) An electron transport layer is prepared on the surface of the active layer. The preparation method of the electron transport layer includes: dissolving 1.5 mg PDINN in 1.5 ml methanol solution and stirring thoroughly to obtain a PDINN solution with a concentration of 1.0 mg / mL; spin-coating the PDINN solution onto the surface of the active layer at a spin speed of 2000 rpm and a spin time of 40 s.

[0067] (6) Fabricating a metal electrode layer on the surface of the electron transport layer, wherein the method for fabricating the metal electrode layer includes: placing the aforementioned substrate / anode / hole transport layer / active layer / electron transport layer in the evaporation stage of an organic vapor deposition system, and evacuating the vacuum to 5×10 -5 At Pa below 1, an Ag electrode of 150 nm was obtained by vapor deposition at 1 Å / s.

[0068] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this embodiment were tested under standard test conditions (AM 1.5 G illumination). These data are shown in Table 1.

[0069] Example 2 In this embodiment, the battery is: PEN / ITO / 4PADCB / PM6:D18-CL:L8-BO:BTP-eC9 (1wt% Lipoicacid-PEG-acid) / PDINN / Ag, which includes, from bottom to top: PEN substrate (0.125nm), ITO anode (60nm), hole transport layer 4PADCB (35nm), active layer (150nm), electron transport layer PDINN (20nm) and metal electrode layer Ag (150nm).

[0070] Methods for preparing flexible organic solar cells containing crosslinking agents with adjustable crosslinking properties include: (1~3) are the same as steps (1~3) in Example 1.

[0071] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6, D18-CL, L8-BO, and BTP-eC9 (mass ratio of 0.9:0.1:0.2:1) in chloroform, adding 1 wt% of Lipoic acid-PEG-acid, heating and stirring at 55°C for 3 h to obtain an active layer solution with a concentration of 16 mg / ml, spin-coating the active layer solution onto the surface of the hole transport layer at a spin speed of 3500 rpm for 30 s, and then annealing at 100°C for 10 min.

[0072] (5~6) are the same as steps (5~6) in Example 1.

[0073] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this embodiment were tested under standard test conditions (AM 1.5 G illumination). These data are shown in Table 1.

[0074] Example 3 In this embodiment, the battery is: PEN / ITO / 4PADCB / PM6:D18-CL:L8-BO:BTP-eC9 (6wt% Lipoicacid-PEG-acid) / PDINN / Ag, which includes, from bottom to top: PEN substrate (0.125nm), ITO anode (60nm), hole transport layer 4PADCB (35nm), active layer (150nm), electron transport layer PDINN (20nm) and metal electrode layer Ag (150nm).

[0075] Methods for preparing flexible organic solar cells containing crosslinking agents with adjustable crosslinking properties include: (1~3) are the same as steps (1~3) in Example 1.

[0076] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6, D18-CL, L8-BO, and BTP-eC9 (mass ratio of 0.9:0.1:1:0.2) in chloroform, adding 6wt% of Lipoic acid-PEG-acid, heating and stirring at 55°C for 3h to obtain an active layer solution with a concentration of 16mg / ml, spin-coating the active layer solution onto the surface of the hole transport layer at a spin speed of 3500rpm for 30s, and then annealing at 100°C for 10min.

[0077] (5~6) are the same as steps (5~6) in Example 1.

[0078] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this embodiment were tested under standard test conditions (AM 1.5 G illumination). These data are shown in Table 1.

[0079] Example 4 In this embodiment, the battery is: PEN / ITO / 4PADCB / PM6:D18-CL:L8-BO:BTP-eC9 (10wt% Lipoicacid-PEG-acid) / PDINN / Ag, which includes, from bottom to top: PEN substrate (0.125nm), ITO anode (60nm), hole transport layer 4PADCB (35nm), active layer (150nm), electron transport layer PDINN (35nm) and metal electrode layer Ag (150nm).

[0080] Methods for preparing flexible organic solar cells containing crosslinking agents with adjustable crosslinking properties include: (1~3) are the same as steps (1~3) in Example 1.

[0081] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6, D18-CL, L8-BO, and BTP-eC9 (mass ratio of 0.9:0.1:0.2:1) in chloroform, adding 10wt% of Lipoic acid-PEG-acid, heating and stirring at 55°C for 3h to obtain an active layer solution with a concentration of 16mg / ml, spin-coating the active layer solution onto the surface of the hole transport layer at a spin speed of 3500rpm for 30s, and then annealing at 100°C for 10min.

[0082] (5~6) are the same as steps (5~6) in Example 1.

[0083] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this embodiment were tested under standard test conditions (AM 1.5 G illumination). These data are shown in Table 1.

[0084] Example 5 In this embodiment, the battery is: PEN / ITO / 4PADCB / PM6:BTP-eC9 (3wt% Lipoic acid-PEG-acid) / PDINN / Ag, which includes, from bottom to top: PEN substrate (0.125mm), ITO anode (60nm), hole transport layer 4PADCB (35nm), active layer (150nm), electron transport layer PDINN (20nm) and metal electrode layer Ag (150nm).

[0085] Methods for preparing flexible organic solar cells containing crosslinking agents with adjustable crosslinking properties include: (1~3) are the same as steps (1~3) in Example 1.

[0086] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6 and BTP-eC9 (mass ratio of 1:1.2) in chloroform, adding 3wt% of Lipoic acid-PEG-acid, heating and stirring at 55°C for 3h to obtain an active layer solution with a concentration of 16mg / ml, spin-coating the active layer solution onto the surface of the hole transport layer at a spin speed of 3500rpm for 30s, and then annealing at 100°C for 10min.

[0087] (5~6) are the same as steps (5~6) in Example 1.

[0088] Example 6 In this embodiment, the battery is: PEN / ITO / 4PADCB / PM6:D18-CL:L8-BO:BTP-eC9 (4wt% Lipoicacid-PEG-acid) / PDINN / Ag, which includes, from bottom to top: PEN substrate (0.125mm), ITO anode (60nm), hole transport layer 4PADCB (35nm), active layer (150nm), electron transport layer PDINN (20nm) and metal electrode layer Ag (150nm).

[0089] Methods for preparing flexible organic solar cells containing crosslinking agents with adjustable crosslinking properties include: (1~3) are the same as steps (1~3) in Example 1.

[0090] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6, D18-CL, L8-BO, and BTP-eC9 (mass ratio of 0.9:0.1:0.2:0.8) in chloroform, adding 4wt% of Lipoic acid-PEG-acid, heating and stirring at 55°C for 3h to obtain an active layer solution with a concentration of 16mg / ml, spin-coating the active layer solution onto the surface of the hole transport layer at a spin speed of 3500rpm for 30s, and then annealing at 100°C for 10min.

[0091] (5~6) are the same as steps (5~6) in Example 1.

[0092] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this embodiment were tested under standard test conditions (AM 1.5 G illumination). These data are shown in Table 1.

[0093] Example 7 In this embodiment, the battery is: PEN / ITO / 4PADCB / PM6:D18-CL:L8-BO:BTP-eC9 (4wt% Lipoicacid-PEG-acid) / PDINN / Ag, which includes, from bottom to top: PEN substrate (0.125mm), ITO anode (60nm), hole transport layer 4PADCB (35nm), active layer (150nm), electron transport layer PDINN (20nm) and metal electrode layer Ag (150nm).

[0094] Methods for preparing flexible organic solar cells containing crosslinking agents with adjustable crosslinking properties include: (1~3) are the same as steps (1~3) in Example 1.

[0095] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6, D18-CL, L8-BO, and BTP-eC9 (mass ratio of 1:0.2:0.2:0.8) in chloroform, adding 4wt% of Lipoic acid-PEG-acid, heating and stirring at 55°C for 3h to obtain an active layer solution with a concentration of 16mg / ml, spin-coating the active layer solution onto the surface of the hole transport layer at a spin speed of 3500rpm for 30s, and then annealing at 100°C for 10min.

[0096] (5~6) are the same as steps (5~6) in Example 1.

[0097] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this embodiment were tested under standard test conditions (AM 1.5 G illumination). These data are shown in Table 1.

[0098] Comparative Example 1 This comparative battery, PEN / ITO / 4PADCB / PM6:D18-CL:L8-BO:BTP-eC9 / PDINN / Ag, comprises, from bottom to top: a PEN substrate (0.125 mm), an ITO anode electrode (60 nm), a hole transport layer 4PADCB (35 nm), an active layer (150 nm), an electron transport layer PDINN (20 nm), and a metal electrode layer Ag (150 nm).

[0099] Methods for fabricating flexible organic solar cells include: (1~3) are the same as steps (1~3) in Example 1.

[0100] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6, D18-CL, L8-BO, and BTP-eC9 (mass ratio of 0.9:0.1:0.2:1) in chloroform to obtain an active layer solution with a concentration of 16 mg / ml. The active layer solution is then spin-coated onto the surface of the hole transport layer at a spin speed of 3500 rpm for 30 s, and then annealed at 100°C for 10 min.

[0101] (5~6) are the same as steps (5~6) in Example 1.

[0102] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this comparative example were tested under standard test conditions (AM 1.5 G illumination). The data are shown in Table 1.

[0103] Comparative Example 2 This comparative battery, PEN / ITO / 4PADCB / PM6:BTP-eC9 / PDINN / Ag, comprises, from bottom to top: a PEN substrate (0.125 mm), an ITO anode (60 nm), a hole transport layer 4PADCB (35 nm), an active layer (150 nm), an electron transport layer PDINN (20 nm), and a metal electrode layer Ag (150 nm).

[0104] Methods for fabricating flexible organic solar cells include: (1~3) are the same as steps (1~3) in Example 5.

[0105] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6 and BTP-eC9 (mass ratio of 1:1.2) in chloroform to obtain an active layer solution with a concentration of 16 mg / ml, spin coating the active layer solution onto the surface of the hole transport layer at a spin coating speed of 3500 rpm and a spin coating time of 30 s, and then annealing at 100°C for 10 min.

[0106] (5~6) are the same as steps (5~6) in Example 5.

[0107] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this comparative example were tested under standard test conditions (AM 1.5 G illumination). The data are shown in Table 1.

[0108] Comparative Example 3 This comparative battery, PEN / ITO / 4PADCB / PM6:D18-CL:L8-BO:BTP-eC9 (4wt% PEG) / PDINN / Ag, consists of, from bottom to top: a PEN substrate (0.125mm), an ITO anode (60nm), a hole transport layer 4PADCB (35nm), an active layer (150nm), an electron transport layer PDINN (20nm), and a metal electrode layer Ag (150nm).

[0109] Methods for fabricating flexible organic solar cells include: (1~3) are the same as steps (1~3) in Example 1.

[0110] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6, D18-CL, L8-BO, and BTP-eC9 (mass ratio of 0.9:0.1:1:0.2) in chloroform, adding 4wt% PEG, heating and stirring at 55°C for 3h to obtain an active layer solution with a concentration of 16mg / ml, spin-coating the active layer solution onto the surface of the hole transport layer at a spin speed of 3500rpm for 30s, and then annealing at 100°C for 10min.

[0111] (5~6) are the same as steps (5~6) in Example 1.

[0112] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this comparative example were tested under standard test conditions (AM 1.5 G illumination). The data are shown in Table 1.

[0113] Comparative Example 4 This comparative battery, PEN / ITO / 4PADCB / PM6:D18-CL:L8-BO:BTP-eC9 (4wt% PEG-COOH-(2000)) / PDINN / Ag, consists of, from bottom to top: a PEN substrate (0.125mm), an ITO anode (60nm), a hole transport layer 4PADCB (35nm), an active layer (150nm), an electron transport layer PDINN (20nm), and a metal electrode layer Ag (150nm).

[0114] Methods for fabricating flexible organic solar cells include: (1~3) are the same as steps (1~3) in Example 1.

[0115] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6, D18-CL, L8-BO, and BTP-eC9 (mass ratio of 0.9:0.1:0.2:1) in chloroform, adding 4wt% PEG-COOH-(2000), heating and stirring at 55°C for 3h to obtain an active layer solution with a concentration of 16mg / ml, spin-coating the active layer solution onto the surface of the hole transport layer at a spin speed of 3500rpm for 30s, and then annealing at 100°C for 10min.

[0116] (5~6) are the same as steps (5~6) in Example 1.

[0117] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this comparative example were tested under standard test conditions (AM 1.5 G illumination). The data are shown in Table 1.

[0118] Comparative Example 5 This comparative battery, PEN / ITO / 4PADCB / PM6:D18-CL:L8-BO:BTP-eC9(4wt% LA+PEI+PEG-COOH) / PDINN / Ag, consists of, from bottom to top: a PEN substrate (0.125mm), an ITO anode (60nm), a hole transport layer 4PADCB (35nm), an active layer (150nm), an electron transport layer PDINN (20nm), and a metal electrode layer Ag (150nm).

[0119] Methods for fabricating flexible organic solar cells include: (1~3) are the same as steps (1~3) in Example 1.

[0120] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6, D18-CL, L8-BO, and BTP-eC9 (mass ratio of 0.9:0.1:0.2:1) in chloroform, then adding 4wt% LA+PEI+PEG-COOH, heating and stirring at 55°C for 3h to obtain an active layer solution with a concentration of 16mg / ml, spin-coating the active layer solution onto the surface of the hole transport layer at a spin speed of 3500rpm for 30s, and then annealing at 100°C for 10min.

[0121] (5~6) are the same as steps (5~6) in Example 1.

[0122] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this comparative example were tested under standard test conditions (AM 1.5 G illumination). The data are shown in Table 1.

[0123] Comparative Example 6 This comparative battery, PEN / ITO / 4PADCB / PM6:D18-CL:L8-BO:BTP-eC9 (4wt% LA) / PDINN / Ag, consists of, from bottom to top: a PEN substrate (0.125 mm), an ITO anode (60 nm), a hole transport layer 4PADCB (35 nm), an active layer (150 nm), an electron transport layer PDINN (20 nm), and a metal electrode layer Ag (150 nm).

[0124] Methods for fabricating flexible organic solar cells include: (1~3) are the same as steps (1~3) in Example 1.

[0125] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6, D18-CL, L8-BO, and BTP-eC9 (mass ratio of 0.9:0.1:0.2:1) in chloroform, adding 4wt% Lipoic acid (LA), heating and stirring at 55°C for 3 hours to obtain an active layer solution with a concentration of 16 mg / ml, spin-coating the active layer solution onto the surface of the hole transport layer at a spin speed of 3500 rpm for 30 seconds, and then annealing at 100°C for 10 minutes.

[0126] (5~6) are the same as steps (5~6) in Example 1.

[0127] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this comparative example were tested under standard test conditions (AM 1.5 G illumination). The data are shown in Table 1.

[0128] Comparative Example 7 This comparative battery, PEN / ITO / 4PADCB / PM6:D18-CL:L8-BO:BTP-eC9 (4wt% alpha-lipoicacid-NHS) / PDINN / Ag, consists of, from bottom to top: a PEN substrate (0.125mm), an ITO anode (60nm), a hole transport layer 4PADCB (35nm), an active layer (150nm), an electron transport layer PDINN (20nm), and a metal electrode layer Ag (150nm).

[0129] Methods for fabricating flexible organic solar cells include: (1~3) are the same as steps (1~3) in Example 1.

[0130] (4) An active layer is prepared on the surface of the hole transport layer. The preparation method of the active layer includes: dissolving PM6, D18-CL, L8-BO, and BTP-eC9 (mass ratio of 0.9:0.1:1:0.2) in chloroform, adding 4wt% alpha-lipoic acid-NHS, heating and stirring at 55°C for 3 hours to obtain an active layer solution with a concentration of 16 mg / ml, spin-coating the active layer solution onto the surface of the hole transport layer at a spin speed of 3500 rpm for 30 seconds, and then annealing at 100°C for 10 minutes.

[0131] (5~6) are the same as steps (5~6) in Example 1.

[0132] The photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and fill factor performance data of the flexible organic solar cell prepared in this comparative example were tested under standard test conditions (AM 1.5 G illumination). The data are shown in Table 1.

[0133] Table 1. Performance Data of Flexible Organic Solar Cells According to Table 1 and Figures 1-6 It is evident that the flexible organic solar cell of the present invention possesses good photovoltaic and mechanical properties.

[0134] according to Figure 5 It can be seen that the uncrosslinked sample in Comparative Example 1 fractured at ~3.70% strain, with a maximum stress of only ~11 MPa; while the fracture point of the crosslinked sample in Example 1 was delayed to 5.15%, and the peak stress increased to ~18 MPa, representing increases of ~45% (elongation) and ~64% (strength), respectively. This indicates that the crosslinked network can effectively limit the formation and propagation of cracks under extreme mechanical strain, effectively enhance the stress transfer and energy dissipation capabilities between chain segments, and significantly suppress the initiation and propagation of cracks under high strain, thereby endowing flexible organic solar cells with superior mechanical reliability.

[0135] The efficiency deformation factor (EDF) is also introduced to comprehensively evaluate the photovoltaic performance and mechanical robustness of the active layer film. It is defined as EDF = PCE × COSFOW, where PCE comes from the photoelectric conversion efficiency of the corresponding blend film flexible device. The highest efficiency quaternary active layer system is selected for comparison, and COSFOW comes from... Figure 5 The crack initiation strain was determined by tensile testing of the thin film on a water surface. The EDF values ​​of the quaternary blend films in Comparative Example 1 and Example 1 were 0.675 and 0.968, respectively, with the latter being almost 1.5 times that of the former, demonstrating that in-situ crosslinking significantly improves the overall performance of flexible organic solar cells (F-OSC). according to Figure 6 It can be seen that the gray curve (Comparative Example 2, PM6:BTP-eC9) only achieved 27.50 mA / cm². 2 The short-circuit current density was 0.834 V, the open-circuit voltage was 75.46%, the fill factor was 75.46%, and the power conversion efficiency (PCE) was 17.32%. After doping the same binary system with 3 wt% Lipoic acid-PEG-acid (red curve, Example 5), the cross-linked network suppressed interfacial recombination and improved carrier extraction, increasing the PCE to 17.74%, attributed to the increase in open-circuit voltage and fill factor. Extending the active layer to a quaternary system of PM6:D18-CL:L8-BO:BTP-eC9 (blue curve, Comparative Example 1) further broadened the absorption and optimized energy level matching, increasing the short-circuit current to 28.01 mA / cm² and the PCE to 18.27%. If 4 wt% crosslinking agent is added to the quaternary system (green curve, Example 1), the short-circuit current and open-circuit voltage increase to 28.93 mA / cm² and 0.847 V, respectively, while the fill factor remains at 76.70%, and the overall efficiency reaches 18.80%, an improvement of approximately 8.5% compared to the baseline device. This demonstrates that the introduction of the crosslinking agent and the third and fourth components enables better phase separation, suppresses trap-assisted recombination, improves charge transfer capability, optimizes the active layer morphology to reduce trap state density, and enhances exciton dissociation and collection processes, thereby improving the open-circuit voltage, short-circuit current density, and fill factor. Simultaneously, without sacrificing mechanical flexibility, it significantly improves the overall performance of the flexible organic solar cell, ultimately achieving high power conversion efficiency. Furthermore, after 5000 bending cycles, the PCE still exceeds 96%.

[0136] In summary, this invention includes a donor material, an acceptor material, and an active layer of Lipoic acid-PEG-acid for flexible organic solar cells, which can significantly improve the photovoltaic and mechanical properties of flexible organic solar cells, enabling them to maintain excellent performance under varying operating environments.

[0137] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0138] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0139] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties, characterized in that, The flexible organic solar cell comprises, from bottom to top: a substrate, a positive electrode, a hole transport layer, an active layer, an electron transport layer, and a metal electrode; The active layer comprises 1-10 wt% lipoic acid-polyethylene glycol-carboxyl groups; The active layer further includes a donor material and an acceptor material, wherein the donor material is selected from PM6, D18, PTQ10 and / or PCE10, and the acceptor material is selected from Y6, N3, Y6-BO, BTP-eC9 and / or L8-BO.

2. The flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties according to claim 1, characterized in that, The groups of the lipoic acid-polyethylene glycol-carboxyl group include: cyclic disulfide bonds, -NH-CO-, -OCH2CH2- and -COOH.

3. The flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties according to claim 1, characterized in that, The structural formula of the lipoic acid-polyethylene glycol-carboxyl group is shown in formula (1). Equation (1), Where n is between 2 and 30.

4. The flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties according to claim 1, characterized in that, The active layer is prepared by mixing donor material, acceptor material, lipoic acid-polyethylene glycol-carboxyl group and organic solvent, heating and stirring, and then spin-coating and annealing.

5. The flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties according to claim 1, characterized in that, The substrate is a flexible substrate, selected from polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyimide (PI), cyclic olefin polymer (COP), or ultrathin flexible glass (UTG).

6. The flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties according to claim 1, characterized in that, The anode is selected from indium tin oxide (ITO), indium tin fluoride (FTO), or aluminum-doped zinc oxide (AZO).

7. The flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties according to claim 1, characterized in that, The hole transport layer is selected from [2-(9H-carbazole-9-yl)ethyl]phosphonic acid, [4-(9H-carbazole-9-yl)butyl]phosphonic acid, [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid, [4-(7H-dibenzo[c,g]carbazole-7-yl)butyl]phosphonic acid, [4-(3,11-dimethoxy-7H-dibenzo[c,g]carbazole-7-yl)butyl]phosphonic acid, [2,7-dimethoxy-9-hydro-carbon-azol-9-yl)methyl]phosphonic acid, [2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanovinyl]phosphonic acid, [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid, or [2-(3,6-dimethoxy-9H-carbazole-9-yl)butyl]phosphonic acid.

8. A method for preparing a flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties as described in claim 1, characterized in that, The preparation method includes: (1) Pretreatment of flexible substrate; (2) Attach a positive electrode to the surface of a flexible substrate and perform surface treatment; (3) A hole transport layer is formed on the surface of the anode, wherein the method for forming the hole transport layer includes: spin-coating a hole transport layer solution onto the surface of the anode and then annealing it; (4) An active layer is formed on the surface of the hole transport layer. The method for preparing the active layer includes: mixing a donor material, an acceptor material, lipoic acid-polyethylene glycol-carboxyl group and an organic solvent to obtain an active layer solution, and then spin-coating the active layer solution onto the surface of the hole transport layer and annealing it. (5) An electron transport layer is formed on the surface of the active layer, wherein the method for forming the electron transport layer includes spin-coating an electron transport layer solution onto the surface of the active layer; (6) Fabricate metal electrodes on the surface of the electron transport layer.

9. The method for preparing a flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties according to claim 8, characterized in that, The surface treatment in (2) includes cleaning and plasma surface treatment, and the plasma surface treatment time is 1~20min.

10. The method for preparing a flexible organic solar cell containing a crosslinking agent with adjustable crosslinking properties according to claim 8, characterized in that, The preparation method of the active layer solution in (4) includes: mixing donor material, acceptor material, 1~10wt% thioctic acid-polyethylene glycol-carboxyl group and organic solvent in a mass ratio of 1:1.2, heating and stirring to obtain an active layer solution with a concentration of 10~30mg / mL.

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