Perovskite passivation using atomic layer deposition

Abstract

A method of passivating a perovskite is provided, the method comprising functionalizing a perovskite layer comprising a perovskite with hydroxyl groups to provide a functionalized perovskite layer comprising the hydroxyl groups bound to the perovskite; and exposing the functionalized perovskite layer to cycles of alternating pulses of a metal precursor and an oxygen precursor under conditions to induce reactions which form a metal oxide layer bound to the functionalized perovskite layer via atomic layer deposition (ALD). Perovskite optoelectronic devices comprising a passivated perovskite layer are also provided.

Description

Atty. Dkt. No. 00100-0402-PCTPEROVSKITE PASSIVATION USING ATOMIC LAYER DEPOSITION CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. provisional patent application number 63 / 721,804 that was filed November 18, 2024, the entire contents of which are incorporated herein by reference.REFERENCE TO GOVERNMENT RIGHTS

[0002] This invention was made with government support under grant number DE-EE0010502 awarded by the Department of Energy. The government has certain rights in the inventionBACKGROUND

[0003] The bandgap tunability in metal halide perovskites enables their integration into tandem solar cells with power conversion efficiencies (PCEs) exceeding the theoretical limit for single-junction solar cells. State-of-the-art all-perovskite tandem solar cells are made in p-i-n architecture using fullerene derivatives, such as Ceo and phenyl-C61 -butyric acid methyl ester (PCBM), as the electron charge transport layer (ETL). However, the mobile ions from the perovskite lattice readily migrate to the fullerene-derivative layers, leading to local charge accumulation and formation of undesirable 1° and Pb° defects, which reduce the conductivity of the fullerene-derivatives and induce non-radiative recombination. Click or tap here to enter tex! Moreover, the migrated ions can further travel to metal electrodes, corroding them to high resistive layers that are barriers to efficient charge extraction. Click or tap here io enter text. These processes worsen over time, hindering the performance and long-term operational stability of all-perovskite tandem solar cells.SUMMARY

[0004] The present disclosure provides methods for passivating perovskite layers using atomic layer deposition (ALD) of a metal oxide (e.g., AI2O3) onto a functionalized perovskite surface (e.g., a OH-functionalized perovskite surface). Although some ALD techniques have been developed for perovskite solar cells, results have been inconsistent and deficiencies have been reported including: insufficient inhibition of migrating halide ions of the perovskite layer into other functional layers (e.g., electron transport layers); decomposition ofAtty. Dkt. No. 00100-0402-PCTorganic ions of the perovskite layer; and formation of halide impurities. The present disclosure includes an Example, below, which demonstrates an illustrative method that addresses each of these deficiencies. The illustrative method is based on the ALD growth of aluminum oxide (AI2O3) onto a carboxyl-functionalized perovskite surface provided by treatment with 5-ammonium valeric acid iodide (5-AVAI). This approach achieved unexpectedly high suppression off and Br migration into a Ceo electron transport layer in contact with the perovskite surface by over an order of magnitude compared to a control. In addition, significant enhancement of the overall stability of a PSC including the protected perovskite was also achieved. Wide bandgap perovskite solar cells (WBG PSCs) with a bandgap of 1.78 eV retained 90% of their initial PCE under continuous illumination for 615 hours at 25 °C. The same devices retained 90% of their maximum PCE during aging under 1 sun illumination at 55 °C over 1000 hours. In addition, a PCE of 27.1% in an all-perovskite tandem solar cell was also achieved.

[0005] An embodiment 1 is a method of passivating a perovskite, the method comprising functionalizing a perovskite layer comprising a perovskite with hydroxyl groups to provide a functionalized perovskite layer comprising the hydroxyl groups bound to the perovskite; and exposing the functionalized perovskite layer to cycles of alternating pulses of a metal precursor and an oxygen precursor under conditions to induce reactions which form a metal oxide layer bound to the functionalized perovskite layer via atomic layer deposition (ALD).

[0006] An embodiment 2 is according to embodiment 1, wherein the hydroxyl groups are provided by activating ligands bound to the perovskite, the activating ligands comprising the hydroxyl groups.

[0007] An embodiment 3 is according to embodiment 2, The method of claim 2, wherein the activating ligands further comprise linking groups covalently bound to the hydroxyl groups and perovskite binding groups covalently bound to the linking groups.

[0008] An embodiment 4 is according to embodiment 3, wherein the linking groups are linear alkyl groups and the perovskite binding groups are ammonium groups.

[0009] An embodiment 5 is according to embodiment 2, wherein the activating ligands are selected from those having formula+ELN — R — (CO)nOH or a salt thereof, wherein R is an alkyl and n is 1 or 0.

[0010] An embodiment 6 is according to embodiment 5, wherein R is a linear alkyd.Atty. Dkt. No. 00100-0402-PCT

[0011] An embodiment 7 is according to embodiment 2, wherein the activating ligands comprise 5-ammonium valeric acid or a salt thereof.

[0012] An embodiment 8 is according to any of embodiments 1-7, wherein the metal oxide layer is an aluminum oxide layer.

[0013] An embodiment 9 is according to any of embodiments 1-8, wherein the ALD is carried out at a growth temperature of at least 75 °C.

[0014] An embodiment 10 is according to any of embodiments 2. 8, or 9. wherein the activating ligands are selected from those having formula H3N — R — COOH, wherein R is a linear alkyl and further wherein the metal oxide layer is an aluminum oxide layer.

[0015] An embodiment 11 is according to any of embodiments 1-10, wherein the activating ligands comprise 5-ammonium valeric acid or a salt thereof.

[0016] An embodiment 12 is according to any of embodiments 1-11, wherein the method provides a passivated perovskite that reduces halide ion migration out of the passivated perovskite by a factor of at least 10 as compared to an unpassivated control perovskite layer.

[0017] An embodiment 13 is a perovskite optoelectronic device comprising a passivated perovskite layer comprising a functionalized perovskite layer comprising a perovskite and a metal oxide layer bound to the functionalized perovskite layer via — O — linkages provided by deprotonated hydroxyl groups bound to the perovskite of the functionalized perovskite layer.

[0018] An embodiment 14 is according to embodiment 13, wherein the deprotonated hydroxyl groups are provided by activating ligands bound to the perovskite of the functionalized perovskite layer.

[0019] An embodiment 15 is according to embodiment 14, wherein the activating ligands further comprise linking groups covalently bound to the deprotonated hydroxyl groups and perovskite binding groups covalently bound to the linking groups.

[0020] An embodiment 16 is according to embodiment 15, wherein the linking groups are linear alkyl groups and the perovskite binding groups are ammonium groups.

[0021] An embodiment 17 is according to embodiment 14, wherein the activating ligands are selected from those having formula H?N — R — (CO)nOH or a salt thereof, wherein R is a linear alkyl and n is 1 or 0.Atty. Dkt. No. 00100-0402-PCT

[0022] An embodiment 18 is according to embodiment 14, wherein the activating ligands comprise 5-ammonium valeric acid or a salt thereof.

[0023] An embodiment 19 is according to any of embodiments 13-18, wherein the metal oxide layer is an aluminum oxide layer.

[0024] An embodiment 20 is according to any of embodiments 13-19, configured as a perovskite solar cell comprising a hole transport layer, an electron transport layer, and the passivated perovskite layer between the hole transport layer and the electron transport layer, wherein the metal oxide layer is located at an interface formed between the electron transport layer and the passivated perovskite layer.

[0025] Other principal features and advantages of the disclosure will become apparent to those skilled in the art upon review of the following drawings, the detailed description, and the appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Illustrative embodiments of the disclosure will hereafter be described with reference to the accompanying drawings.

[0027] FIG. 1 A is a schematic showing a bare perovskite surface exposed to trimethyl aluminum (TMA) and water during the ALD-AI2O3 deposition (left image) and further showing a functionalized perovskite surface (with 5-ammonium valeric acid, 5-AVAI) exposed to TMA and water during the ALD-AI2O3 deposition. FIG. IB shows XRD spectra of control perovskite films (control = no passivation ligands, no 5-AVAI functionalization, and no ALD-AI2O3 deposition; control / AI2O3 = no passivation ligands, no 5-AVAI functionalization, and ALD-AI2O3 deposition) and perovskite films with passivation ligands (either PEAI or BAI) and ALD-AI2O3 deposition (1) and (2); and perovskite films with 5-AVAI functionalization and ALD-AI2O3 deposition (3). FIG. 1C shows ToF-SIMS spectra corresponding to perovskite films (l)-(3)before and after AI2O3 deposition. FIG. ID shows PCEs of a control PCS, PCSs with passivation ligands before and after ALD-AI2O3 deposition (l)-(2) and PCSs with 5-AVAI functionalization before and after ALD-AI2O3 deposition.

[0028] FIG. 2A shows PLQY data from the control (untreated), AI2O3 only (sample 1) 5-AVAI only (sample 2), and 5-AVAI+AI2O3 (sample 3) perovskite films on quartz and HTL (NiOx and Me-4PACz) substrates, as well as full device stacks (HTL / perovskite / Ceo). FIG.Atty. Dkt. No. 00100-0402-PCT2B shows transient photoluminescence traces for these films on glass substrates. FIGS. 2C-2E show the PL intensity distribution of 1 mm2perovskite films of (FIG. 2C) control, (FIG.2D) AI2O3 only and (FIG. 2E) 5-AVAI+AI2O3. FIGS. 2F-2H show Kelvin probe force microscopy of perovskite films of (FIG. 2F) control, (FIG. 2G) AI2O3 only and (FIG. 2H) 5-AVAI+AI2O3.

[0029] FIG. 3 A shows a schematic of a WBG solar cell (target device). FIG. 3B shows J-V curves of a control device (without passivation and without AI2O3). FIG. 3C shows a histogram of Voc, Jsc, FF, and PCE of control versus target for 8 devices. The device's active area was 0.049 cm2. FIG. 3D shows ToF-SIMS spectra of the control device and the target device after open circuit aging at 85 °C under 1 sun illumination for 72 hours. FIG. 3E shows maximum power point (MPP) tracking of ingle-junction WBG control and target devices under continuous AM 1.5G illumination. Devices were encapsulated, and MPP tracking was carried out under ambient air at 25 °C for 615 hours and subsequently at 55 °C for 1000 hours conditions.

[0030] FIG. 4A shows a schematic diagram of an all-perovskite tandem device structure. FIG. 4B shows a cross-sectional scanning electron microscopy (SEM) image of the tandem device. FIG. 4C shows J-V curves of the WBG subcell, NBG subcell, and tandem devices. FIG. 4D shows power output of the tandem device for 150 s, exhibiting a stabilized PCE of 26.7%. FIG. 4E shows EQE spectra of WBG and NBG subcells within the tandem devices. FIG. 4F shows maximum power point (MPP) tracking of the tandem device under continuous AM 1.5G illumination. The device was encapsulated, and MPP tracking was carried out under ambient air at 25 °C conditions.DETAILED DESCRIPTION

[0031] The present disclosure provides methods for passivating perovskite layers, which may be used in a variety of perovskite optoelectronic devices. Such a method comprises functionalizing a perovskite layer with hydroxyl (OH) groups to provide a functionalized perovskite layer; and exposing the functionalized perovskite layer to cycles of alternating pulses of a metal precursor and an oxygen precursor under conditions to induce reactions which form a metal oxide layer on the functionalized perovskite layer via atomic layer deposition (ALD).Atty. Dkt. No. 00100-0402-PCT

[0032] The perovskite layer comprises (or consists) of a perovskite, which refers to a chemical compound having a perovskite structure such as ABX3. In embodiments, A is a protonated amine or an alkali metal ion; B is a divalent metal ion; and X is an anion capable of bonding to B. A variety of protonated amines may be used, e.g., a primary ammonium, a secondary' ammonium, a tertiary ammonium, a quaternary ammonium, or an iminium.Suitable illustrative protonated amines include, e.g.. NH4+(ammonium); CH3NH3 (methylammonium, MA); CH(NH2)2+(formamidinium, FA); (CH3)2NH2+(dimethylammonium); (CH3CH2)NH3+(ethylammonium); (NH2FC (guanidinium); and (CHstybT (tetramethylammonium). A variety of alkali metal ions may be used, e.g., Cs+. A variety of divalent metal ions may be used, e.g., a post-transition metal or a metalloid such as Ge2+. Sn2+. or Pb2+. A variety of anions may be used, e.g.. a halide such as F’, Cl’, Br , or I’.

[0033] The term “perovskite” (as well as the formula ABX-) encompasses alloys including more than one type of A in varying relative amounts (provided the sum of the amounts is about 1); more than one type of B in varying relative amounts (provided the sum of the amounts is about 1); more than one type of X in vary ing relative amounts (provided the sum of the amounts is about 3); and combinations thereof.

[0034] Illustrative perovskites are provided in the Example, below, and include narrow bandgap perovskites such as Cso.1FAo.6MAo3Pbo.5Sno.5I3; and wide bandgap perovskites such as Cso.2FAo.8Pb(lo.63Bro.37)3.

[0035] As noted above, the present methods comprise functionalizing a perovskite with hydroxyl groups. The term “hydroxyl group” encompasses the chemical entity “OH” as well as an OH group that is part of another chemical entity such as a carboxyl group (COOH). That is, “hydroxyl group” encompasses the hydroxyl group of a carboxyl group. The hydroxyl groups may be provided by activating ligands. Activating ligands refer to chemical compounds comprising the hydroxyl groups and which are capable of binding to the desired perovskite.

[0036] A suitable activating ligand comprises (or consists of) the hydroxyl group (e.g., — OH or — COOH), a linking group covalently bound to the hydroxyl group, and a perovskite binding group covalently bound to the linking group. The exact chemical composition of the activating ligand, including the linking group and the perovskite binding group, depends upon the desired perovskite. However, an illustrative linking group is an alkyl group. The alkyl group may be a linear alkyl group having, e.g., from 2 to 8 carbon atoms. This includes 3, 4,Atty. Dkt. No. 00100-0402-PCT5, 6, 7 carbon atoms as well as a range of between any of the disclosed number of carbon atoms. An illustrative perovskite binding group is a cationic group such as an ammonium group ( — NH3+). In both the hydroxyl group and the ammonium group, the “ — ” represents the covalent bond to the linking group, which may be a direct covalent bond, e.g., to a carbon atom of an alkyl linking group. In embodiments, the activating ligand is selected from those having formula H?N — R — (CO)nOH, wherein R is alkyl and n is 0 or 1. Illustrative activating ligands are provided in the Example, below, and include 5-ammonium valeric acid.

[0037] The term “activating ligands” encompasses the ionic form thereof as well as the salt form in which a counter ion may be present, such as a halide, e.g., I". A single type of activating ligand or multiple, different types of activating ligands may be used.

[0038] Functionalization of the perovskite layer may be carried out by exposing the desired perovskite layer to a solution comprising the activating ligands (e.g., by spin coating) under conditions to bind the activating ligands to the perovskite via their perovskite binding groups. Conditions of the exposure, including concentration of the activating ligands in the solution, may be adjusted to facilitate binding, achieve a desired degree of functionalization (including surface coverage of the perovskite layer with the activating ligands), as well as to achieve a desired property for an optoelectronic device comprising the perovskite layer (e.g., power conversion efficiency, PCE; maximum reduction in halide ion migration, maximum increase in carrier lifetime, etc.). Illustrative functionalization conditions are provided in the Example, below.

[0039] As described in the Example below, functionalizing the perovskite layer as described herein provides active sites for the subsequent ALD growth of the metal oxide layer thereon. Prior to conducting the experiments described in this Example, it was unpredictable whether the hydroxyl groups of the activating ligands would serve as such active sites or would, instead, interact with the underlying perovskite layer. The ALD growth involves exposing the functionalized perovskite layer to cycles of alternating pulses of the metal precursor and the oxygen precursor under conditions to induce reactions which form the metal oxide layer. The metal oxide layer may be, but need not be, a continuous metal oxide layer. That is, in some embodiments, the metal oxide layer may be in the form of discrete islands over the perovskite layer, connected to the perovskite layer via the activating ligands. “Metal precursor” refers to a molecule comprising the metal of the desired metal oxide layer and “oxygen precursor” refers to a molecule comprising oxygen. The metal oxideAtty. Dkt. No. 00100-0402-PCTlayer may be an aluminum oxide layer which may be grown via ALD by using various organoaluminium compounds, e.g., trimethylaluminum, as the aluminum precursor and, e.g., water as the oxygen precursor. The number of cycles and other conditions (growth temperature, growth time) may be adjusted to provide a desired surface coverage of metal oxide, a desired thickness of the metal oxide layer, as well as to achieve a desired property for an optoelectronic device comprising the perovskite layer. However, in embodiments, the growth temperature is at least 75 °C, at least 85 °C, at least 95 °C, at least 100 °C, or a range of between any of these values. Other illustrative ALD growth conditions are provided in the Example, below.

[0040] ALD growth on a functionalized perovskite is schematically illustrated in FIG. 1 A (right image). Although not show n in the figure, the A1(OH)2 groups of neighboring activating ligands may further react, forming Al-O-Al bonds with the elimination of water. This results in a metal oxide layer bound to the underlying perovskite via — O — linkages provided by the activating ligands.

[0041] The passivated perovskite layers formed according to the present methods are also encompassed. A passivated perovskite layer comprises a functionalized perovskite layer and a metal oxide layer bound to the functionalized perovskite layer via — O — linkages. As noted above, these — O — linkages may be provided by a plurality of activating ligands bound to the perovskite of the functionalized perovskite layer. Any of the disclosed perovskites, metal oxides, and activating ligands may be used. In this context, the term “activating ligands” may refer to the deprotonated version thereof, in view of the reaction of the hydroxyl groups during the ALD growth of the metal oxide layer.

[0042] The passivated perovskite layers may be incorporated into optoelectronic devices. Although a variety of perovskite optoelectronic devices (e.g., light-emitting diodes, lasers, detectors, sensors) may be used, in embodiments, the optoelectronic device is a perovskite solar cell. A perovskite solar cell may comprise a hole transport layer, an electron transport layer, and any of the disclosed passivated perovskite layers between the hole transport layer and the electron transport layer. The passivated surface of the perovskite layer, and thus, the metal oxide layer, may be located at an interface formed between the passivated perovskite layer and the electron transport layer.

[0043] For perovskite solar cells, various materials may be used in the hole transport layer (e.g., carbazole-based self-assembled monolayers (SAMs), poly(3,4-Atty. Dkt. No. 00100-0402 -PCTethylenedioxythiophene) polystyrene sulfonate (PEDOTPSS)) and the electron transport layer (e.g., buckminsterfullerene, Ceo, and its derivatives such as PCBM). Any other material layers typically used in perovskite solar cells may be included, e.g., a substate (e.g., glass, indium tin oxide, fluorine-doped tin oxide), contacts (e.g., various metals), a hole blocking layer (e.g., bathocuproine), an electron blocking layer, etc. The perovskite solar cells may be configured according to a particular architecture such as an inverted (pin) architecture in which the perovskite solar cell is illuminated through the electron transport layer. The perovskite solar cell may be a single junction or a multijunction device (e.g., a tandem device). An illustrative single junction device is show n in FIG. 3 A and an illustrative tandem device is shown in FIG. 4A.

[0044] Perovskite solar cells comprising the present passivated perovskite layers are characterized by high PCEs which may be tested as described in the Example, below. (See FIGS. 3C and 4C.)

[0045] The present passivated perovskite layers are also characterized by reduced ion migration (e.g., halide ion migration) from the perovskite into neighboring functional layers (e.g., into an electron transport layer). Time-of-flight secondary ion mass spectroscopy may be used to quantify reductions in halide ion migration as described in the Example, below. Moreover, this Example demonstrates that present approach to perovskite passivation achieves unexpectedly large reductions in halide ion (e.g., 1, Br) migration. Specifically, as shown in FIG. 3D, the illustrative passivated perovskite layer reduced halide ion migration by over an order of magnitude (i.e., more than 10 times) as compared to an unpassivated control perovskite layer. By “unpassivated control perovskite layer.” it is meant the same perovskite layer as the passivated perovskite layer and fabricated in the same way except without the activating ligand functionalization and without the ALD grown metal oxide layer. Thus, the present passivated perovskite layers may be characterized as reducing halide ion migration out of the perovskite by at least a factor of 7, ate least a factor of 10, at least a factor of 12, or a range between any of these values, as compared to an unpassivated control perovskite layer.

[0046] The present passivated perovskite layers are also characterized by increased carrier lifetimes, which may be quantified using time-resolved photoluminescence as described in the Example, below-. Again this Example demonstrates that present approach to perovskite passivation achieves unexpectedly large increases in carrier lifetime. Specifically, as shown in FIG. 2B, the illustrative passivated perovskite layer increased carrier lifetime by¬Atty. Dkt. No. 00100-0402-PCTover a factor of five as compared to an unpassivated control perovskite layer. Thus, the present passivated perovskite layers may be characterized as exhibiting carrier lifetimes that are at least 5 times greater, at least 7 times greater, at least 9 times greater, or a range between any of these values, as compared to an unpassivated control perovskite layer.

[0047] The present passivated perovskite layers are also characterized by the absence of BX2 (e.g., Pbb) impurities which can arise as the perovskite degrades during ALD growth. (See FIG. IB, bottommost trace.)

[0048] Methods of using the present perovskite optoelectronic devices are also provided. The methods comprise illuminating any of the disclosed perovskite optoelectronic devices with light to generate charge carriers, and collecting the charge carriers.EXAMPLE

[0049] Introduction

[0050] This Example describes formation of a protective barrier layer on a perovskite surface using ALD. It was found that conventional passivation ligands could not survive after being subjected to ALD deposition at 100 °C. Without wishing to be bound to any particular theory, it was hypothesized that the instability of conventional passivation ligands during ALD was due to the lack of ALD active sites, which leads to poor seeding with ALD precursors, causing the passivation ligands to evaporate at 100 °C. It was found that linear chain carboxyl -ammonium molecules were able to provide ALD active sites for Al-0 bonding, consequently eliminating the instability. Specifically, 5-ammonium valeric acid iodide (5 -AV Al) was used to functionalize a perovskite surface with carboxyl (-COOH) groups which preferentially bind with ALD precursors during AI2O3 deposition. Chck or tap here to enter text. It was further found that the 5-AVAI not only prevented perovskite degradation but also enabled uniform deposition of AI2O3 on perovskites, confirmed by photoluminescence (PL) mapping and kelvin probe force microscopy (KPFM). This resulted in a more compact and robust barrier layer against ion migration, leading to improved solar cell stability: an encapsulated WBG solar cell showed negligible degradation in ambient air under maximum power point (MPP) tracking under one-sun illumination at 25 °C for 615 h. Subsequently, the same device retained 90% of its maximum PCE during aging under 1 sun illumination at 55 °C over 1000 hours.

[0051] Materials and MethodsAtty. Dkt. No. 00100-0402-PCT

[0052] All materials were used as received without further purification. Commercial ITO substrates (20 Q / sq) with 25 mm x 25 mm dimensions were purchased from TFD Inc. The organic halide salts (formamidinium iodide (FAI), methylammonium iodide (MAI), and formamidinium bromide (FABr)) were purchased from GreatCell Solar Materials (Australia). Pbl2(99.99%), PbBn (99.999%), CsBr (>99.0%), and [4-(3,6-Dimethyl-9H-carbazol-9-yl)butyl]phosphonic Acid (Me-4PACz) were purchased from TCI Chemicals. CsI (99.999%) was purchased from Sigma-Aldrich. CTo was purchased from Xi’an Polymer Light Technology (China). All the solvents used in the process were anhydrous and purchased from Sigma-Aldrich.

[0053] Perovskite precursor solutions

[0054] Wide bandgap perovskite. A 1.05 M wide-bandgap perovskite precursor solution with a composition of Cso.2FAo.8Pb(Io.63Bro.37)3 was prepared by dissolving CsI, CsBr, FAI, FABr, PbBr2 and Pbh in mixed solvents of DMF and DMSO with a volume ratio of 4: 1. The precursor solution was stirred at 60 °C for Ih and then filtered using a 0.22 pm PTFE membrane before use.

[0055] Narrow bandgap perovskite. A 1.8 M narrow-bandgap perovskite precursor solution with a composition of Cso.1FAo.6MAo.3Pbo.5Sno.5I3 was prepared by dissolving CsI, FAI, MAI, Snh, and Pbh in the mixed solvents of DMF and DMSO with a volume ratio of 3:1. Additives including tin powders (5 mg / ml), GuaSCN (4 mg / ml), SnF2 (14 mg / ml), and GlyHCl (4 mg / ml), were added to the precursor solution. The precursor solution was stirred for 1 h at 45 °C and then filtered using a 0.22 pm PTFE membrane before use.

[0056] Solar cell fabrication

[0057] Single junction wide bandgap perovskite solar cell. A NiOx nanoparticle solution (purchased from Avantama) layer was first spin-coated onto ITO substrates at 4000 rpm for 25 s in the air without any post-treatment, and then the substrates were immediately transferred to the glovebox. The NiOx solution was diluted using ethanol with a ratio of 10: 1. Me-4PACz (0.3 mg / ml) in ethanol was spin-coated on the NiOx film at 4000 rpm for 25 s and then annealed at 100 °C for 10 min. For the perovskite film fabrication, the substrate was spun at 4000 rpm for 32 s with an acceleration of 1000 rpm; 100 pL of anisole was dropped onto the substrate during the last 10 s of the spinning. The substrates were then transferred onto a hotplate and heated at 100 °C for 15 min. The surface treatment was finished by depositing 100 pL of 5-Ammonium valeric acid iodide (5-AVAI) solution (1 mg / ml) onto theAtty. Dkt. No. 00100-0402-PCTperovskite film surface at a spin rate of 4000 rpm for 25 s with a 1000 rpm / s acceleration. The film was then annealed at 100 °C for 5 min. After cooling down to room temperature, the substrates were then transferred to the atomic layer deposition (ALD) system (Arradiance) to deposit 10 cycles of AI2O3 at 100 °C using precursors of trimethylaluminum (TMA) and deionized (DI) water. The pulse and purge time of TMA was 60 ms and 50 s with a 40 seem of N2 flow. The pulse and purge time of DI water was 60 ms and 50 s with a 40 seem of N2 flow. After cooling down to room temperature, the substrates were transferred to the evaporation system, and 30-nm thick Ceo film was subsequently deposited on top by thermal evaporation at a rate of 0.2 A / s. The substrates were then transferred to the atomic layer deposition (ALD) system (Savaanah) to deposit 15 nm SnCh at 100 °C using precursors of tetrakis(dimethylamino) tin (iv) (99.9999%) and deionized water. A 140 nm Ag electrode was then deposited by thermal evaporation.

[0058] All-perovskite tandem solar cells. The wide bandgap perovskite solar cell fabrication was completed as described above up through the deposition of ALD-SnCh. After the ALD deposition of SnCh. 1 nm of Au was deposited by thermal evaporation. Next, PEDOT:PSS (diluted at a 1 :2 volume ratio in IPA) was spin-coated onto the WBG subcell at 4,000 rpm for 30 seconds and then annealed at 120 °C for 10 minutes in the air. After cooling, the substrates were transferred to a nitrogen-filled glovebox for the deposition of the NBG subcell. The NBG perovskite precursor solution was spin-coated onto the substrates at 1,000 rpm for 10 seconds, followed by 3,800 rpm for 45 seconds. During the second spincoating step, 400 pL of toluene was poured onto the substrate 20 seconds before the end. The substrate was then annealed at 100 °C for 10 minutes. Post-treatment with EDA was carried out by spin-coating a solution of 1 pL EDA in 20 ml of CBZ at 4,000 rpm for 25 seconds, followed by annealing at 100 °C for 5 minutes. Finally, Ceo (27 nm), BCP (7 nm), and Ag (140 nm) were sequentially thermally evaporated.

[0059] Device testing

[0060] The current density -voltage (J-F) characteristics for the fabricated solar cells were measured using a Keithley 2450 source meter under illumination from a solar simulator (Newport, Class A Oriel Sol2A) with a light intensity of 100 mW / cm2(confirmed with a calibrated reference solar cell from Newport, 91150V). J-V curves were measured under nitrogen flow' with a scanning rate of 100 mV / s (voltage step of 10 mV and delay time of 200 ms). The active area was determined by the aperture shade mask (0.049 cm2for small-areaAtty. Dkt. No. 00100-0402-PCTdevices) placed in front of the solar cell and was identical to the contact area. Encapsulated substrates contained 4 devices each. EQE measurements were performed in ambient air using an X system with monochromatic light focused on the device pixel and a chopper frequency of 20 Hz. For tandem solar cells, EQE measurements were performed in ambient air and the bias illumination from bright LEDs with emission peaks of 845 and 470 nm was used for the measurements of the front and back subcells, respectively. No bias voltage was applied during the EQE measurements of the tandem solar cells.

[0061] Characterization

[0062] XRD was carried out by a Rigaku Miniflex diffractometer (Cu Kai radiation). Time-resolved photoluminescence (TRPL) measurements were conducted using an Edinburgh FS5 spectrofluorometer with a 373 nm excitation laser. The PL decay curves were fitted by a biexponential decay function. Photoluminescent (PL) mapping was carried out by using the Horiba LabRam HR Evolution. Through confocal PL, comprehensive mapping of the large area was achieved to assess the uniformity of perovskite and aluminum oxide samples, both with and without AVAL A 473 nm laser, a 5x objective lens, and a neutral density filter (ND filter: 0.01%) were utilized to minimize phase separation in the spectra, acquiring each spectrum with a 0.1 s exposure time using a 600 gr / mm grating. For the KPFM measurements, the Bruker Icon was employed using a Pt / Si coated tip with a spring constant of 1.6 N / m and a frequency of 61 kHz. Images were processed using Nanoscope software, including flattening of all potential images and application of a low-pass filter. The scanning rates were set at 0.1 or 0.2 Hz. High-resolution SEM images were obtained using the Hitachi S8030 microscope with an accelerating voltage of 3 kV. ToF-SIMS measurements were carried out on an IONTOF M6 instrument with a primary Bi source of 30 keV and an analysis area of 50 x 50 pm2.

[0063] Direct ALD-AI2O3 growth on the perovskite films with different passivation ligands

[0064] ALD-AI2O3 was first deposited on perovskite films at temperatures from 60-100 °C (including 60 °C, 75 °C, and 100 °C), and X-ray diffraction (XRD) spectra were measured (data not shown). For the AI2O3 layer deposited at 100 °C, a notable Pbh peak was observed upon AI2O3 deposition. This peak was also observed in the 60 °C and 75 °C spectra at reduced intensities. These results indicated that the ALD precursors (trimethyl aluminum, TMA), and the oxidant (DI water) damaged the perovskite films during the depositionAtty. Dkt. No. 00100-0402-PCTprocess (which is schematically illustrated in FIG. 1A without 5-AVAI functionalization (left)). As noted above, the PbL peak diminished as the ALD temperature decreased which indicates the degradation can be alleviated by reducing the process temperature, as this reduces the reactivity of the precursor and oxidant Chck or tap here to enter text. However, a reduction in reaction temperature also leads to decreased uniformity of the AI2O3 layer due to less reactivity'. Click or tap here io enter text. An approach was sought to adequately stabilize the perovskite surface to avoid decomposition during the ALD process at high temperatures.

[0065] In an initial set of experiments, passivation ligands were used to evaluate protection of the perovskite films (as well as to passivate the perovskite surface).Phenethylammonium iodide (PEAI) and n-butylammonium iodide (BAI) were selected (chemical structures not shown). These passivation ligands have an ammonium (-NH3 ) group that anchors to the perovskite surface and an additional functional groups (e.g., benzene and methyl, respectively) that extend away from the perovskite surfaced lick or tap here to enter text FIG. IB shows XRD spectra of the control film and the perovskite films with passivation ligands before and after AI2O3 deposition. It was observed that films with PEAI and BAI showed the Pbh peak (*) after AI2O3 deposition, revealing that these passivation ligands do not protect the perovskite films during the ALD process ( additional data not shown).

[0066] Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) was used to analyze the presence of passivation ligands on the perovskite surface before and after AI2O3 deposition (FIG. 1C, (1) and (2)). However, evidence of PEA+and BA+on perovskite films could not be found after AI2O3 deposition. This is believed to be due to the instability of PEA+and BA+, which deprotonate in FA+-containing perovskite at high temperatures, e.g., above 85 °C. Click or tap here to enter iexl.

[0067] Therefore, a different approach was examined involving functionalization of the perovskite surface to enable favorable binding sites for ALD precursor seeding and to protect perovskite from damage during ALD. A carboxyl-ammonium ligand, 5-AVAI, was selected: the carboxyl group provided seeding sites for ALD growth, while the ammonium group interacted with the perovskite, confirmed via contact angle measurement (data not shown). Click or tap here to enter text. Unlike the perovskite films with the passivating ligands, it was observed that films with 5-AVAI functionalization did not show the Pbb peak after AI2O3 deposition (FIG. IB, (3) and other data not shown). The ToF-SIMSAtty. Dkt. No. 00100-0402-PCTmeasurements also found that the 5-AVA+cation was able survived during ALD-AI2O3 deposition at 100 °C. indicating that it acts as a buffer layer that adequately prevents perovskite degradation during the ALD process at 100 °C (FIG. 1C, (3)). This is believed to be due to the TMA precursor’s methyl groups (-CH3) which prefer to react with the carboxyl group, resulting in strong Al-0 bonds (see the right schematic in FIG. lA).Click or tap here ■0 enter text Consequently, the chemical Al-0 bonds act as robust capping layer that prevents 5-AVA+from evaporating during the ALD process. As shown in FIG. ID, , the photovoltaic performance of the various PSCs was examined. The 5-AVAI treatment led to a remarkable improvement in PCE following AI2O3 deposition. By contrast, the PSCs using the passivation ligands along with ALD-AI2O3 showed suppressed PCEs due to the Pbh formed after ALD-AI2O3 deposition.

[0068] Uniform ALD-AI2O3 passivation for reducing nonradiative recombination at the perovskite / Ceo

[0069] Notably, it was found that 5-AVAI functionalization played a key role in both ALD-oxide uniformity and the reduction of nonradiative recombination at the interface between the perovskite and Ceo. To investigate the impact of interface defect passivation by ALD-AI2O3, photoluminescence quantum yield (PLQY) measurements were conducted. As shown in FIG. 2A, it was found that the control and samples 1-3 exhibited only slight improvements in PLQY for perovskite films on quartz and HTL substrates. However, while the control perovskite film exhibited a drop in PLQY of nearly 2 orders of magnitude upon the addition of Ceo (full stack), samples 1-3 reduced the magnitude of this loss. In particular, ALD-AI2O3 after 5-AVAI treatment (sample 3) reduced the magnitude of the loss the most. FIG. 2B shows the steady-state PL and time-resolved photoluminescence (TRPL), showing enhanced carrier lifetimes, indicating reduced nonradiative recombination. Specifically, the carrier lifetimes of the control, AI2O3 (sample 1) 5-AVAI (sample 2), and ALD-AI2O3 after 5-AVAI treatment (sample 3) were 16.9, 12.8, 39.4, and 122.7 ns, respectively. This shows that the AI2O3 film deposited after 5-AVAI treatment possessed a significantly less defective surface compared to the control and sample 1 and 2 films.

[0070] In FIGS. 2C-2E, the millimeter-scale photoluminescence (PL) intensity distribution of the perovskite films was evaluated to investigate the uniformity of AI2O3 deposition on the perovskite surface with and without 5-AVAI treatment. Compared to the control film (FIG. 2C), there were localized areas where the PL intensity was enhanced afterAtty. Dkt. No. 00100-0402-PCTAI2O3 deposition even without 5-AVAI treatment (FIG. 2D). However, with 5-AVAI treatment, the overall PL intensity was not only improved, but also the distribution was more uniform (FIG. 2E). This demonstrates that the 5-AVAI functionalization also facilitates a more uniform deposition of AI2O3 on the perovskite film . Additionally, the kelvin probe force microscopy (KPFM) images show n in FIGS. 2F-2H further demonstrate that ALD-AI2O3 after 5-AVAI treatment narrowed the potential distribution (3.60 mV compared with 5.17 mV for the control), again demonstrating a more uniform AI2O3 deposition. This is believed to be due to the -COOH groups on the perovskite surface providing ALD active sites, resulting in a substantially more uniform AI2O3 deposition. The uniform AI2O3 layer, in turn, prevented direct contact betw een Ceo and perovskite, resulting in the suppression of overall nonradiative recombination.

[0071] Performance and stability of WBG perovskite solar cells

[0072] Single-junction wide bandgap (WBG) perovskite solar cells were then fabricated with a bandgap of 1.78eV (FIG. 3 A). A device structure of glass-ITO / NiOx / Me-4PACz / 1.05 M Cso.2FAo.8Pb(Io.63Bro.37)3 perovskite / S-AVAI / ALD-ALO / Ceo / ALD-SnCh / Ag was utilized. The J-V curves of the WBG control device are shown in FIG. 3B. Compared to the control device (1.24 V and 77.9%) (no 5-AVAI functionalization and no ALD-AI2O3), the target device (1.31V and 83.1%) exhibited a substantially higher Fbc,FF, and PCE (FIG. 3C). The current density (J sc) and 1.78 eV bandgap were confirmed with an external quantum efficiency (EQE) measurement (data not shown).

[0073] It was found that the 5-AVAI functionalization followed by ALD-AI2O3 significantly suppressed the ion migration throughout the target devices. The ion migration in control and target devices was tracked via ToF-SIMS after open circuit conditions with aging at 85 °C under 1 sun illumination for 72 hours (FIG. 3D). The control device (no 5-AVAI functionalization and no ALD-AI2O3) showed that Ag 10ns migrated to the perovskite layer. In addition, halide anions such as I and Br ions migrated from the perovskite layer to the ETL and electrodes. Br ions are known to have a smaller size and higher diffusivity than I ions, resulting in the poor stability performance of WBG devices, ( lick or tap here to enter text AI2O3 deposition on the control film (no 5-AVAI functionalization), some ion migration was suppressed (data not shown). However, when AI2O3 was deposited on 5-AVAI treated perovskite (target device), the ion migration was substantially suppressed. Specifically, compared to the control device, the target device show ed an order of magnitude fewer ionsAtty. Dkt. No. 00100-0402-PCTincluding Ag, I, and Br at the interface between ETL and perovskite. This is believed to be due to a more uniform and compact AI2O3 layer that more strongly protects against ion migration, as also confirmed in FIGS. 2A-2H and discussed above.

[0074] The ion migration behavior in target devices as a function of different ALD processing temperatures (60°C, 80°C, and 100°C) was also investigated. The higher-temperature processed device showed the greatest suppression of ion migration owing to more uniform AI2O3 deposition at higher temperatures (data not shown). Suppressed ion migration was also observed by comparing the mobile ion concentration (No) of control and target devices using a transient dark cunent measurement (data not shown). Finally, the improvements due to suppressed ion migration led to enhanced stability for the target WBG PSC, which exhibited negligible changes in device efficiency with -99% of the maximum PCE under continuous 1-sun illumination near the maximum power point (MPP) at 25 °C over 615 hours. (FIG. 3E.) As shown in this figure, the same device was further tested at 55 °C and showed retention of about 90% of its maximum PCE during aging under 1 sun illumination over 1000 hours. These stabi 1 i ty results are substantially greater than other ambient air stability reports for encapsulated WBG PSCs around Eg of 1.78 eV(datanot shown).

[0075] All-perovskite tandem solar cells

[0076] The WBG active layer was then incorporated into monolithic all-perovskite tandem solar cells in combination with a 1.8 M CS005FA0.7MA0.25Pb0.5Sn0.5I3 of -1.2 eV NBG perovskite. The tandem device structure used was glass-ITO / NiOx / Me-4PACz / WBG perovskite / 5-AVAI / ALD-Al203 / C6o / ALD-SnOx / Au 1 nm / PEDOT:PSS / NBG perovskite / Cso / ALD-SnOx / Ag (FIG. 4A). The scanning electron microscopy (SEM) cross-sectional image is shown in FIG. 4B. FIG. 4C shows J-V scans of the WBG subcell, NBG subcell, and tandem devices. A PCE of 27.1 % with a Voc of 2.11 V was achieved, along with a Jsc of 16.0 mA / cm2and an FF of 80.4%. From EQE measurements of each subcell, the integrated Jsc values of 15.5 mA / cm2and 15.2 mA / cm2were obtained, respectively. The calculated bandgap of the WBG and NBG subcells from EQE spectra w ere 1.78 eV and 1.24 eV. respectively. The tandem device retained 90% of its initial PCE, limited by the NBG cell, after 500 h of continuous operation under AM 1.5G illumination, as shown in FIG. 4F.

[0077] ConclusionAtty. Dkt. No. 00100-0402-PCT

[0078] In summary', this Example presents a strategy' for a robust and compact ion migration barrier layer for PSCs by depositing a uniform ALD-AI2O3 layer on a perovskite surface functionalized with carboxyl groups using 5-AVAI. This functionalized perovskite surface prevented degradation during ALD deposition at 100 °C and facilitated the formation of a uniform ALD-AI2O3 layer, resulting in significantly improved device performance. Consequently, ALD-AI2O3 on carboxyl-functionalized perovskite resulted in a more compact and robust barrier layer against ion migration, enhancing WBG solar cell stability, achieving ~90% of initial PCE after 615 hours at 25 °C and after 1000 hours at 55 °C using MPP tracking under 1 sun illumination. Finally, the improved WBG perovskite was integrated into an all-perovskite tandem, achieving a PCE of 27.1 %. This approach enables high-efficiency and stable perovskite-based solar cells and represents a significant step toward the practical application of this technology.

[0079] Additional information regarding this Example, including information referenced as being not shown and the like, may be found in U.S. provisional patent application number 63 / 721,804 that was filed November 18, 2024, the entire contents of which are incorporated herein by reference.

[0080] The word "illustrative" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "illustrative" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Further, for the purposes of this disclosure and unless otherwise specified, "a" or "an" means "one or more.”

[0081] The foregoing description of illustrative embodiments of the disclosure has been presented for purposes of illustration and of description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosure. The embodiments were chosen and described in order to explain the principles of the disclosure and as practical applications of the disclosure to enable one skilled in the art to utilize the disclosure in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the claims appended hereto and their equivalents.

[0082] If not already included, all numeric values of parameters in the present disclosure are proceeded by the term “about” which means approximately. This encompasses those variations inherent to the measurement of the relevant parameter as understood by those ofAtty. Dkt. No. 00100-0402-PCTordinary skill in the art. This also encompasses the exact value of the disclosed numeric value and values that round to the disclosed numeric value.

[0083] The term “type” as used herein refers to chemical formula such that a single type means the same chemical formula and different type means different chemical formula. Similarly, use of “more” as in “one or more” refers to use of different types of the relevant entity.

[0084] Any instance of the term “comprising” (and the like) may be replaced with the term “consisting” (and the like).

Claims

Atty. Dkt. No. 00100-0402-PCTWHAT IS CLAIMED IS:

1. A method of passivating a perovskite, the method comprising functionalizing a perovskite layer comprising a perovskite with hydroxyl groups to provide a functionalized perovskite layer comprising the hydroxyl groups bound to the perovskite; and exposing the functionalized perovskite layer to cycles of alternating pulses of a metal precursor and an oxygen precursor under conditions to induce reactions which form a metal oxide layer bound to the functionalized perovskite layer via atomic layer deposition (ALD).

2. The method of claim 1. wherein the hydroxyl groups are provided by activating ligands bound to the perovskite, the activating ligands comprising the hydroxyl groups.

3. The method of claim 2. wherein the activating ligands further comprise linking groups covalently bound to the hydroxyl groups and perovskite binding groups covalently bound to the linking groups.

4. The method of claim 3. wherein the linking groups are linear alkyl groups and the perovskite binding groups are ammonium groups.

5. The method of claim 2, wherein the activating ligands are selected from those having formula+H3N — R — (CO)nOH or a salt thereof, wherein R is an alkyl and n is 1 or 0.

6. The method of claim 5, wherein R is a linear alkyl.

7. The method of claim 2. wherein the activating ligands comprise 5-ammonium valeric acid or a salt thereof.

8. The method of claim 1, wherein the metal oxide layer is an aluminum oxide layer.

9. The method of claim 1, wherein the ALD is carried out at a growth temperature of at least 75 °C.Atty. Dkt. No. 00100-0402-PCT10. The method of claim 2, wherein the activating ligands are selected from those having formula HsN — R — COOH, wherein R is a linear alkyl and further wherein the metal oxide layer is an aluminum oxide layer.

11. The method of claim 10, wherein the activating ligands comprise 5-ammonium valeric acid or a salt thereof.

12. The method of claim 1, wherein the method provides a passivated perovskite that reduces halide ion migration out of the passivated perovskite by a factor of at least 10 as compared to an unpassivated control perovskite layer.

13. A perovskite optoelectronic device comprising a passivated perovskite layer comprising a functionalized perovskite layer comprising a perovskite and a metal oxide layer bound to the functionalized perovskite layer via — O — linkages provided by deprotonated hydroxyl groups bound to the perovskite of the functionalized perovskite layer.

14. The perovskite optoelectronic device of claim 13, wherein the deprotonated hydroxyl groups are provided by activating ligands bound to the perovskite of the functionalized perovskite layer.

15. The perovskite optoelectronic device of claim 14, wherein the activating ligands further comprise linking groups covalently bound to the deprotonated hydroxyl groups and perovskite binding groups covalently bound to the linking groups.

16. The perovskite optoelectronic device of claim 15, wherein the linking groups are linear alkyl groups and the perovskite binding groups are ammonium groups.

17. The perovskite optoelectronic device of claim 14, wherein the activating ligands are selected from those having formula "FhN — R — (CO)nOH or a salt thereof, wherein R is a linear alkyl and n is 1 or 0.

18. The perovskite optoelectronic device of claim 14, wherein the activating ligands comprise 5-ammonium valeric acid or a salt thereof.

19. The perovskite optoelectronic device of claim 13, wherein the metal oxide layer is an aluminum oxide layer.Atty. Dkt. No. 00100-0402-PCT20. The perovskite optoelectronic device of claim 13 configured as a perovskite solar cell comprising a hole transport layer, an electron transport layer, and the passivated perovskite layer between the hole transport layer and the electron transport layer, wherein the metal oxide layer is located at an interface formed between the electron transport layer and the passivated perovskite layer.

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