PEROVSKITE SOLAR CELLS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Application No. 62/695,350, filed on July 9, 2018, which is hereby incorporated by reference in its entirety for all purposes.

SUMMARY OF THE INVENTION

[0002] Devices having carrier selective interfaces and methods for producing devices having carrier selective interfaces are provided.

[0003] According to various aspects there is provided a photovoltaic device. In some aspects, the photovoltaic device may include: a superstate; a collector formed on the superstate; a cross-linked hole transport layer (HTL) formed on the collector; a perovskite (PVSK) crystal formed on the cross-linked HTL; a diffused interface formed by diffusion of the PVSK into the cross-linked HTL; an electron transport layer (ETL) formed on the PVSK crystal; and a second collector formed on the ETL.

[0004] The superstate may be a rigid glass superstate, a flexible glass superstate, a rigid plastic superstate, or a flexible plastic superstate, and the superstate may be transparent or semi-transparent. The first collector formed on the superstate may be a transparent or semi transparent collector and may be formed from one of indium tin oxide (ITO), thin metal multilayers, and a silver nanowire network. The second collector formed on the ETL may be an opaque collector formed from one of an aluminum foil and a stainless steel foil.

[0005] The cross-linked HTL may be a compound having a formula: HTS-E-R ¹ , where E is a lithium-free electrolyte having a cation component covalently bonded to HTS and R ¹ and an anion component; HTS is a hole transport structure, R ¹ is HTS; or H; or R ² ; or a C1-C20 branched, unbranched, cyclic, or polycyclic monovalent aliphatic group that is saturated or unsaturated and substituted or unsubstituted; or a substituted or unsubstituted monovalent aromatic group that is fused or unfused; and R ² is a reactive cross-linking group. [0006] According to various aspects there is provided a method for forming a photovoltaic device. In some aspects, the method may include: coating a superstrate with a first collector; coating and drying a cross-linkable hole transport material (HTM) solution over the first collector on the superstrate to form a hole transport layer (HTL), wherein the HTM is a cross- linkable HTM ; cross-linking the HTL; coating a perovskite (PVSK) solution on top of the cross-linked HTL to form a diffusion interface between the HTL and the PVSK; crystallizing the PVSK solution; coating an electron transport material (ETM) solution on top of the PVSK to form an electron transport layer (ETL); and evaporating a metal layer on top of the ETL to form a second collector.

[0007] The superstrate may be a rigid glass superstrate, a flexible glass superstrate, a rigid plastic superstrate, or a flexible plastic superstrate, and the superstrate may be transparent or semi-transparent. The first collector formed on the superstrate may be a transparent or semi transparent collector and may be formed from one of indium tin oxide (ITO), thin metal multilayers, and a silver nanowire network. The second collector formed on the ETL may be an opaque collector formed from one of an aluminum foil and a stainless steel foil.

[0008] The cross-linked HTL may be a compound having a formula: HTS-E-R ¹ , where E is a lithium-free electrolyte having a cation component covalently bonded to FITS and R ¹ and an anion component; HTS is a hole transport structure, R ^f is HTS; or H; or R ² ; or a C1-C20 branched, unbranched, cyclic, or polycyclic monovalent aliphatic group that is saturated or un saturated and substituted or unsubstituted; or a substituted or unsubstituted monovalent aromatic group that is fused or unfused; and R ² is a reactive cross-linking group.

[0009] According to various aspects there is provided a photovoltaic device. In some aspects, the photovoltaic device may include: a substrate; a first collector formed on the substrate; a first carrier selective contact layer formed on the first collector; a perovskite (PVSK) crystal formed on the first carrier selective contact layer; a second carrier selective contact layer formed on the PVSK; and a second collector formed on the second carrier selective contact layer. One of the first carrier selective contact layer and the second carrier selective contact layer may be a cross-linked carrier selective contact layer. A diffused interface may be formed by diffusion of the PVSK into the cross-linked carrier selective contact layer.

[0010] The first collector formed on the substrate may be a transparent or semi-transparent collector and may be formed from one of indium tin oxide (ITO), thin metal multilayers, and

9 a silver nanowire network. The second collector formed on the second carrier selective contact layer may be an opaque collector formed from one of an aluminum foil and a stainless steel foil.

[0011] The cross-linked carrier selective contact layer may be a hole transport layer (HTL) formed from a compound having a formula: HTS-E-R ¹ , wherein: E is a lithium-free electrolyte having a cation component covalently bonded to HTS and R ¹ and an anion component; HTS is a hole transport structure; R ¹ is HTS; or H; or R ² ; or a C1-C20 branched, unbranched, cyclic, or polycyclic monovalent aliphatic group that is saturated or un saturated and substituted or unsubstituted; or a substituted or unsubstituted monovalent aromatic group that is fused or unfused; and R ² is a reactive cross-linking group.

[0012] Numerous benefits are achieved by way of the various embodiments over conventional techniques. For example, the various embodiments provide carrier selective interfaces in perovskite solar cells (PSCs) that eliminate delamination of the hole transport layer HTL from the PVSK crystal and provides more efficient charge transfer across the i nterfaces. In some embodiments, cross-linking of the HTM enables direct appl ication of PVSK precursors without dissolution of the HTL. These and other embodiments along with many of its advantages and features are described in more detail in conjunction with the text below and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Aspects and features of the various embodiments will be more apparent by describing examples with reference to the accompanying drawings, in which:

[0014] FIG. 1 is a diagram of a photovoltaic device illustrating a crystal structure of an HTL and a PVSK crystal according to various aspects of the present disclosure;

[0015] FIG. 2 is a diagram illustrating a diffused interface between the HTL and the PVSK according to various aspects of the present disclosure;

[0016] FIG. 3 is a diagram illustrating a superstate configured photovoltaic device with a planar p~i~n structure having a diffused interlace according to various aspects of the present disclosure; [0017] FIG. 4 is a diagram illustrating a first processing method for producing a superstate configured photovoltaic device with a planar p-i-n structure having a diffused interface according to various aspects of the present disclosure;

[0018] FIG. 5 is a diagram illustrating substrate configured photovoltaic device with a planar n~i~p structure having a diffused interlace according to various aspects of the present disclosure; and

[0019] FIG. 6 is a diagram illustrating a second processing method for producing a substrate configured photovoltaic device with a planar n-i-p structure having a diffused interface according to various aspects of the present disclosure.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0020] Modem solar cells sometimes incorporate a layer of perovskite (“PVSK”) that acts as a solar absorber PVSK encompasses a number of different materials, each having the same type of crystal structure as calcium titanium oxide (CaTiCh). Examples include methyl ammonium lead halides, which have a formula of CHsNILPbX, where X is bromine, chlorine or iodine. PVSK increases solar conversion efficiency compared to conventional silicon solar cells PVSK can reduce cost and weight and make flexible (i.e , non-rigid) solar cells. PVSK can be formed on semiconductor materials using various techniques. The world of Perovskite still has not found a suitable non-organic HTM material that allows for high efficiency (i.e., >20%). Typical PVSK efficiency is less than 18%.

[0021] Organic HTMs bring on new problems or their own. For p-i-n structure devices, during photovoltaic device production, wetting of PVSK precursor solutions and PVSK on organic hole transfer materials (HIM) is inferior, resulting in poor adhesion between perovskite and organic HTM. On the other hand, for n-i-p structure devices, the dense PVSK crystal prevents HTM in the hole transfer layer (HTL) that have larger crystal structures from entangling within the PVSK crystal, resulting in PVSK-HTL delamination. For both device structures, thermal morphological instability increases free volume and allows halide and metal migration between contact material and PVSK. Embodiments in accordance with the present disclosure address these and other issues. [0022] Lithium salts may be added to the material to increase conductivity; however, they cause the layer to be less water stable, reactive to the halide in the perovskite, and re-dox active.

[0023] Also, a robust method to passivate the interface between HTM and PVSK is not available using conventional approaches. Current passivation methods contact the PVSK with the polar or ionic groups of otherwise inactive or even interfering polymers and small molecules. But the association is weak and, as a result, the molecules are not fixed with strong bonds, which can result in poor lifetimes.

[0024] FIG. 1 is a diagram of a photovoltaic device 100 illustrating a crystal structure of an HTL 110 and a PVSK crystal 120 according to various aspects of the present disclosure. As can be seen in FIG. 1 , the disparity in crystal size prevents a strong bond from forming between the PVSK 120 and the HTL 110 which can result in eventual delamination 130 of the HTL 110. Further, for n-i-p structures, solvent choices are limited, thus limiting the choice of HTM because the solvent interacts poorly with P VSK.

[0025] According to various aspects of the present disclosure, novel organic HTMs in the p-i-n configuration may be utilized. In the p-i-n configuration, ETMs such as TiCte, Sn0 ₂ , PCBM, ZnO, etc., may be deposited onto PVSK. The choice of a p-i-n structure is favorable because there are more options available to apply an ETM on top of PVSK rather than apply the HTM on top of the PVSK. These materials enable the p-type material to be organic instead of an oxide material.

[0026] Many p-i-n structure devices cannot be realized with organic HTMs because the PVSK solvent would redissolve the HTM. The best working organic HTMs (e g.. PTAA and related polymers) are expensive and, as a result, increase device costs.

[0027] Despite the progress made in solar cell technology, there is a need in the art for improved methods and systems related to PVSK solar cell technology.

[0028] While certain embodiments are described, these embodiments are presented by way of example only, and are not intended to limit the scope of protection. The apparatuses, methods, and systems described herein may be embodied in a variety of other forms.

Furthermore, various omissions, substitutions, and changes in the form of the example methods and systems described herein may be made without departing from the scope of protection. [0029] In a superstrate configured photovoltaic device with a planar p-i-n structure, for example, but not limited to, a solar cell, sunlight enters from a superstrate face and passes thru the HTL first before reaching the PVSK. In order to coat and grow PVSK crystals on top of an HTL (i.e., inverted processing of PVSK on an HTL), the HTL must be insoluble to DMF, DMSO, etc., otherwise, the HTL may be washed away or eroded when the PVSK coating is applied.

[0030] In accordance with various aspects of the present disclosure, the adhesion problem is addressed by employing the ionic interaction of the PVSK with the covalently bonded ionic group in the molecules. Cross-linkable HTMs having small molecules with high

performance values may be coated on the collector, for example, indium tin oxide (!TO) or the like, and then cross-linked to become insoluble. Cross-linking refers to the ability of a reactive group to form covalent bonds (i.e., cross-link) with another, appropriately structured, reactive group, and may be accomplished by introduction of energy (e.g., ultraviolet light, visible light, infrared light, or heat) to drive the cross-linking reaction.

[0031] U.S. Application No. 62/636,329, incorporated herein by reference, provides examples of cross-linkable HTMs that may be used to form HTLs in accordance with the present disclosure. For example, a cross-linkable HTM may be a compound having a formula: HTS-E-R ¹ , where E may be a lithium-free electrolyte having a cation component covalently bonded to the hole transport structure (HTS) and R ¹ and an anion component, HTS is a hole transport structure, R ¹ is a FITS or FI or R or a C1-C20 branched, unbranched, cyclic, or polycyclic monovalent aliphatic group that is saturated or unsaturated and substituted or unsubstituted or a substituted or unsubstituted monovalent aromatic group that is fused or unfused, and R ² may be a reactive cross-linking group.

[0032] Cross-linking the HTL may enable PVSK pre-cursors to be coated directly on top of the HTL without dissolution of the HTL forming a diffused interlace. A diffused interface may enable stronger adhesion between the interfaces. The HTL may be fabricated using nickel oxide (NiOx), barium nickel oxide (BaNiOx) and/or another hole transport material.

The porosity of the HTL can vary from zero to 30 % porous.

[0033] Some embodiments may utilize mesoporous titanium oxide (TiOx), tin oxide (SnOx) and/or another electron transport material as the ETM in a superstrate n-i-p configuration, for example, a PVSK/T1O2 diffused interface. The porosity can vary from 0 to 40 % porous. In some embodiments, the porosity can vary between 5 and 10 %. In other embodiments, porosity of the transport layer may range from 10% to 90% or 10% to 40% or even 15% to 30%. Pore size may be consistent with the typical Graetzel mesoporous T1O2 pore size

[0034] Such an interface may also enable better charge transfer between the two interfaces improving performance of the cell. Further, cross-linking the HTL may minimize thermal morphological instability and excess free volume that enables unwanted halide and metal migration between contact material and PVSK, as well as addressing the issue of HIM solubility in PVSK solvent.

[0035] FIG. 2 is a diagram 200 illustrating a diffused interface between the HTL 210 and the PVSK 260 according to various aspects of the present disclosure. As illustrated in FIG. 2, a cross-linkable HTM may be coated on a collector 220. The collector 220 may be, for example, a transparent or semi-transparent layer of indium tin oxide (ITO) or the like, or on an opaque collector, for example, but not limited to, aluminum foil, stainless steel foil, etc. In accordance with various aspects of the present disclosure, an additional thin (e.g., less than Imih) collector may be deposited onto the metal foil without or without an additional barrier layer in between

[0036] The HTM may be cross-linked, for example, by infrared heating or other introduction of energy. Once cross-linked, PVSK pre-cursors (e.g., PbL·) 230 may be coated directly on top of the HTL 210 without dissolution of the HTL 210. PVSK pre-cursors 230 may flow 240 into the pores of the HTL 210 to forming a diffused interface 250. Cross- linkable HTLs, such as those described in U.S. Application No. 62/636,329 incorporated herein by reference, may offer even higher adhesion to perovskite than traditional interfaces, for example planar n-i-p structure interfaces.

[0037] FIG. 3 is a diagram illustrating a superstate configured photovoltaic device 300 with a planar p-i-n structure having a diffused interface according to various aspects of the present disclosure. As illustrated in FIG. 3, in the superstate configured photovoltaic device 300 with a planar p-i-n structure sunlight impinges on the face of the superstate 310 and passes thru the HTL 330 first before reaching the PVSK 340. Referring to FIG. 3, the superstate configured photovoltaic device 300 may include a superstate 310.

[0038] While FIG. 3 illustrates a glass superstate, one of ordinary skill in the art w ll appreciate that embodiments in accordance with the present disclosure are not limited to this implementation and that other materials may be utilized for the superstate. In accordance with various embodiments of the present disclosure, the superstate may be a rigid or flexible superstate, for example, but not limited to rigid or flexible glass, flexible fiberglass mesh, flexible plastic, etc.

[0039] While not shown in FIG. 3, some embodiments may include an optional barrier layer. The barrier layer may be formed on the superstate 310. The barrier layer may be an insulating barrier layer or a conductive barrier layer. The barrier layer may protect the cell from the environment, e.g., w¾ter and oxygen, and may also keep the volatile components of the PVSK inside. The barrier layer may be formed by alternating layers of inorganic materials like S1O2, AI2O3, and SiN which may be deposited by CVD, PVD, ALD, or atmospheric plasma deposition organic coating for planarization (GCP) layers. Alternatively, sufficient barriers may include deposited single layers of the inorganic layers mentioned above. The barrier layer thickness may be approximately lOOnm.

[0040] A collector 320 may be formed over the superstate 310, or the barrier layer if present. The collector 320 may be a transparent or semi-transparent collector. While FIG. 3 illustrates an indium tin oxide (ITO) collector 320, embodiments in according to the present disclosure are not limited to this implementation. For example, indium tin oxide (ITO) may be used when the substrate is a plastic substrate while fluorine-doped tin oxide (FTO) may be used when the substrate is a glass superstate. In some embodiments, the collector 320 may be other thin metal multilayers or a silver nano wire network.

[0041] A first carrier selective contact layer 330, for example, a cross-linked HTL, formed on the collector 320. The cross-linked HTL may be formed from a cross-linkable HTM such as described above with respect to U.S. Application No 62/636,329. Cross-linking of the HTM enables direct application of PVSK precursors without dissolution of the HTL and provides more efficient charge transfer across the interface. The cross-linkable HTM may be cross-linked by introduction of energy (e.g., ultraviolet light, visible light, infrared light, or heat) to drive the cross-linking reaction

[0042] One of ordinary skill in the art will appreciate that the illustrated embodiment of FIG. 3 is a p-i-n structure. In other embodiments having an n-i-p structure, the first carrier selective contact layer may be formed from an ETM, for example, but not limited to, T1O2, 8nCK PCBM, ZnO, etc,

[0043] In some embodiments, an optional interlayer (not shown) may be formed on the first carrier selective contact layer 330 to enhance efficiency of the PSC. The optional interlayer may be formed from, for example, but not limited to, PCBM, C60, M0O3, reduced graphine oxide, LiF, Pbl?., PbSCN, etc. The interlayer may enhance PSC performance by, for example, plugging pinholes in the PVSK layer, passivating surface electronic defects of the PVSK and/or contact layer, causing better band alignment among layers with appropriate carrier concentration forming space charge regions in more appropriate locations, bonding with halide vacancies to prevent halide migration, preventing formation of oxyhalide complexes, etc.

[0044] A PVSK layer 340 may be formed on the first carrier selective contact layer 330. PVSK as a light absorber layer increases solar conversion efficiency compared to

conventional silicon solar cells. A diffused interface 350 may be formed by diffusion of the PVSK 340 or PVSK precursor into the cross-linked HTL 330. One of ordinary skill in the art will appreciate that the illustrated embodiment of FIG. 3 is an p-i-n structure. In other embodiments having an n-i-p structure, the first carrier selective contact layer may be formed from an ETM, for example, but not limited to, T1O2, SnO?., PCBM, ZnO, etc., and therefore is not cross-linked with the PVSK layer.

[0045] In some embodiments, a second optional interlayer (not shown) may be formed on the P VSK layer 340 to enhance efficiency of the PSC. The optional interlayer may be formed from, for example, but not limited to, PCBM, C60, etc.

[0046] A second carrier selective contact layer 360 may be formed on the PVSK layer 340. For example, in the p-i-n structure illustrated in FIG. 3, the second carrier selective contact layer 360 may be an electron transport layer (ETL). The second carrier selective contact layer 360 may be formed from an ETM, for example, but not limited to, TΪO2, SnCh, PCBM, ZnO, etc.

[0047] In other embodiments having an n-i-p structure, the second earner selective contact layer may be formed from a cross-linkable HΊA4 such as described above with respect to U.S. Application No. 62/636,329. The cross-linkable HTM may be cross-linked by introduction of energy (e.g., ultraviolet light, visible light, infrared light, or heat) to drive the cross-linking reaction. A diffused interface may be formed by diffusion of the PVSK 340 into the cross- linked HTL.

[0048] A second collector 370 may be formed on the second carrier selective contact layer 360. While the second collector 370 is illustrated as an aluminum layer in FIG. 3, embodiments in accordance with the present disclosure are not limited to this

implementation. In other embodiments, the second collector may be, for example, but not limited to, Au, Cu, Ni, stainless steel, Mo, other metals, carbon black, conductive carbon pastes, or another material, formed on the ETL 360. For a superstate configured

photovoltaic device such as that shown in FIG. 3, since light reaches the second collector after passing through the PVSK absorber, the second collector could be optically non transparent, i.e., an opaque collector, for example, but not limited to, e.g., aluminum foil, stainless steel foil, etc.

[0049] FIG. 4 is a diagram illustrating a first processing method 400 for producing an superstate configured photovoltaic device with a planar p-i-n structure having a diffused interface according to various aspects of the present disclosure. With the superstate configured photovoltaic device with a planar p-i-n structure formed by the first processing method 400, sunlight enters from a substrate-face and passes thru the HTL first before reaching the PVSK.

[0050] Referring to FIG. 4, the process may start with a superstate. While FIG. 4 illustrates a glass superstate, embodiments according to the present disclosure are not limited to this implementation. The superstate may be, for example, but not limited to, rigid or flexible glass, rigid, flexible plastic, flexible fiberglass mesh, etc. The superstate may be transparent or semi-transparent. While not shown in FIG. 4, an optional barrier layer may be formed on the superstate.

[0051] At operation 410, the superstate, or barrier layer if present, may he coated with a collector. The collector may be a transparent or semi-transparent collector formed from, for example, but not limited to, gold or PΌ, or another material.

[0052] At operation 415, a cross-linkable HTM solution may be coated and dried over the collector on the superstate, or barrier layer if present. For example, a coating blade may be used to coat the cross-linkable HTM solution over the collector on the superstate, forming an HTL.

[0053] Any of the cross-linkable HTMs disclose by U.S. Application No. 62/636,329 may be used to form cross-linkable HTLs in accordance with the present disclosure. At operation 420, the HTL may be cross-linked. For example, energy may be introduced to the HTL by infrared heating for 1-15 minutes at 100-150°C or another source. While not shown in FIG. 4, in some embodiments an optional interlayer may be formed on the first carrier selective layer. The optional interlayer may be formed from, for example, but not limited to, PCBM, C60, etc. lu [0054] At operation 425, a PVSK solution may be coated on top of the cross-linked HTL. For example, a coating blade may coat the PVSK solution over the cross-linked HTL. By cross-linking the HTL, the HTL is no longer soluble in and is not eroded by the PVSK and the PVSK solution can flow into the pores of the HTL. Accordingly, the diffused interface between the HTL and the PVSK is formed. At operation 430, the PVSK solution may be crystallized. For example, the PVSK solution may be heated and dried resulting in the formation of a PVSK crystal layer on top of the cross-linked HTL.

[0055] While not shown in FIG. 4, in some embodiments a second optional interlayer may be formed on the PVSK crystal layer. The second optional interlayer may be formed from, for example, but not limited to, PCBM, C60, etc. At operation 435, second carrier selective contact layer, for example an electron transport material (ETM) solution, may be coated on top of the PVSK crystal layer. For example, a coating blade may be used to coat the ETM solution on the PVSK crystal layer and the ETM solution may be dried to form an electron transport layer (ETL)

[0056] At operation 440, a second collector may be applied over the ETL. While the second collector is illustrated as an aluminum layer in FIG. 4, embodiments according to the present disclosure are not limited to this implementation. For a superstrate configured photovoltaic device such as that shown in FIG. 4, since light reaches the second collector after passing through the PVSK absorber, the second collector could be optically non transparent, i.e., an opaque collector, for example, but not limited to, e.g., aluminum foil, stainless steel foil, etc., evaporated on top of the ETL to form the second collector.

[0057] FIG. 5 is a diagram illustrating a substrate configured photovoltaic device 500 with a planar n-i-p structure having a diffused interface according to various aspects of the present disclosure. As illustrated in FIG. 5, in the substrate configured photovoltaic device 500 with a planar n-i-r structure sunlight impinges on the transparent thin film metal layer 570 and passes thru the ETL 560 first before reaching the PVSK 540.

[0058] Referring to FIG. 5, the substrate configured photovoltaic device 500 may include a substrate 510. While FIG. 5 illustrates a glass substrate, one of ordinary skill in the art will appreciate that embodiments in accordance with the present disclosure are not limited to this implementation and that other materials may be utilized for the substrate. In some embodiments, the substrate may be an electrically insulating substrate material. In accordance with various embodiments of the present disclosure, the substrate may be a rigid or flexible substrate. In other embodiments, the substrate 510 may be a flexible or rigid electrically conductive substrate material.

[0059] While not shown in FIG. 5, some embodiments may include an optional barrier layer. The barrier layer may be formed on the substrate 510. The barrier layer may be an insulating barrier layer or a conductive barrier layer. The barrier layer may protect the cell from the environment, e.g., water and oxygen, and may also keep the volatile components of the PVSK inside. The barrier layer may be formed by alternating layers of inorganic materials like S1O2, AI2O3, and SiN which may be deposited by CVD, PVD, ALD, or atmospheric plasma deposition organic coating for planarization (GCP) layers. Alternatively, sufficient barriers may include deposited single layers of the inorganic layers mentioned above. The barrier layer thickness may be approximately lOOnm.

[0060] For a conductive substrate an optional thin (e.g., less than 1m) collector 520 may be formed on the optional barrier layer. For an insulating substrate, the collector may necessarily be formed on the optional barrier layer, or on the substrate 510 when a barrier layer is not formed

[0061] For a substrate configured photovoltaic device such as that shown in FIG. 5, since light reaches the substrate after passing through the PVSK absorber, the substrate could he non-transparent, i.e., an opaque collector, for example, but not limited to, e.g., aluminum foil, stainless steel foil, etc. In some embodiments, the collector may be the substrate itself.

[0062] A first carrier selective contact layer 530, for example, a cross-linked HTL for an n-i-p structure, may be formed on the collector 520. The cross-linked HTL may be formed from a cross-linkable HTM such as described above with respect to U.S. Application No. 62/636,329. Cross-linking of the HTM enables direct application of PVSK precursors without dissolution of the HTL and provides more efficient charge transfer across the interface. The cross-linkable HTM may be cross-linked by introduction of energy (e.g., ultraviolet light, visible light, infrared light, or heat) to drive the cross-linking reaction.

[0063] One of ordinary skill in the art will appreciate that the illustrated embodiment of FIG. 5 is an n-i-p structure. In other embodiments having a p-i-n structure, the first carrier selective contact layer may be formed from an ETM, for example, but not limited to, T1O2, SnO··. PCBM, ZnO, etc, [0064] In some embodiments, an optional interlayer (not shown) may be formed on the first carrier selective contact layer 530 to enhance efficiency of the PSC. The optional interlayer may be formed from, for example, but not limited to, PCBM, C60, M0Q3, reduced graphine oxide, LiF, Pbl _? , PbSCN, etc. The interlayer may enhance PSC performance by, for example, plugging pinholes in the PVSK layer, passivating surface electronic defects of the PVSK and/or contact layer, causing better band alignment among layers with appropriate carrier concentration forming space charge regions in more appropriate locations, bonding with halide vacancies to prevent halide migration, preventing formation of oxyhalide complexes, etc.

[0065] A PVSK layer 540 may be formed on the first carrier selective contact layer 530. PVSK as a light absorber layer increases solar conversion efficiency compared to

conventional silicon solar cells. A diffused interface 550 may be formed by diffusion of the PVSK 540 into the cross-linked HTL 530. One of ordinary _' skill in the art will appreciate that the illustrated embodiment of FIG . 5 is an n-i-p structure. In other embodiments having a p- i-n structure, the first carrier selective contact layer may be formed from an ETM, for example, but not limited to, TiCb, SnO?., PCBM, ZnO, etc., and therefore is not cross-linked with the PVSK layer

[0066] In some embodiments, a second optional interlayer (not shown) may be formed on the PVSK layer 540 to enhance efficiency of the PSC. The optional interlayer may be formed from, for example, but not limited to, PCBM, C60, etc.

[0067] A second carrier selective contact layer 560 may be formed on the PVSK layer 340. For example, in the n-i-p structure illustrated in FIG. 5, the second carrier selective contact layer 560 may be an electron transport layer (ETL) The second carrier selective contact layer 560 may be formed from an ETM, for example, but not limited to, TiC , SnO?., PCBM, ZnO, etc.

[0068] In other embodiments having an p-i-n structure, the second carrier selective contact layer may be formed from a cross-linkable HTM such as described above with respect to U.S. Application No. 62/636,329. The cross-linkable HTM may be cross-linked by introduction of energy (e.g., ultraviolet light, visible light, infrared light, or heat) to drive the cross-linking reaction. A diffused interface may be formed by diffusion of the PVSK 540 into the cross- linked HTL. [0069] A second collector 570 may be formed on the second carrier selective contact layer 560. While the second collector 570 is illustrated as in ITO layer in FIG. 5, embodiments in accordance with the present disclosure are not limited to this implementation. In other embodiments, the second collector may be, for example, but not limited to, thin metal multilayers, a silver nanowire network, or another material, formed on the ETL 560. The second collector may be a transparent collector.

[0070] FIG. 6 is a diagram illustrating a second processing method 600 for producing a substrate configured photovoltaic device with a planar n-i-p structure having a diffused interface according to various aspects of the present disclosure. With the substrate configured photovoltaic device with a planar n-i-p structure formed by the second processing method 600, sunlight enters from the transparent thin film metal layer and passes thru the ETL first before reaching the PVSK.

[0071] Referring to FIG. 6, the process may start with a substrate. While FIG. 6 illustrates a glass substrate, embodiments according to the present disclosure are not limited to this implementation. The substrate may be, for example, but not limited to, rigid or flexible glass, rigid or flexible plastic, metal foil, or another material. While not shown in FIG. 6, an optional barrier layer may be formed on the substrate.

[0072] At operation 610, the substrate, or barrier layer if present, may be coated with a collector. The collector may be a transparent or semi-transparent collector formed from, for example, but not limited to, gold or ITO on aluminum foil, or another material. In some embodiments, the collector may be an opaque collector, for example, but not limited to, e.g., aluminum foil, stainless steel foil, etc. In some embodiments, the collector may be the substrate itself.

[0073] At operation 615, first carrier selective contact layer, for example a cross-linkable HTM solution, may be coated and dried over the collector. For example, a coating blade may be used to coat the cross-linkable HTM solution over the transparent collector on the substrate forming an HTL. Any of the cross-linkable HTMs disclosed by U.S. Application No. 62/636,329 may be used to form cross-linkable HTLs in accordance with the present disclosure. At operation 620, the HTL may be cross-linked. For example, energy may be introduced to the HTL by infrared heating for 1-15 minutes at 100-150°C or another source. While not shown in FIG. 6, in some embodiments an optional interlayer may be formed on the first carrier selective layer. The optional interlayer may he formed from, for example, but not limited to, PCBM, C60, etc.

[0074] At operation 625, a PVSK solution may be coated on top of the cross-linked HTL. For example, a coating blade may coat the PVSK solution over the cross-linked HTL. By cross-linking the HTL, the HTL is no longer soluble in and is not eroded by the PVSK and the P VSK solution can flow into the pores of the HTL. Accordingly, a diffused interface between the HTL and the PVSK is formed. At operation 630, the PVSK solution may be crystallized. For example, the PVSK solution may be heated and dried resulting in the formation of a PVSK crystal layer on top of the cross-linked HTL.

[0075] While not shown in FIG. 6, in some embodiments a second optional interlayer may be formed on the PVSK crystal layer. The second optional interlayer may be formed from, for example, but not limited to, PCBM, C60, etc. At operation 635, second earner selective contact layer, for example an electron transport material (ETM) solution, may be coated on top of the PVSK crystal layer. For example, a coating blade may be used to coat the ETM solution on the PVSK crystal layer and the ETM solution may be dried to form an electron transport layer (ETL).

[0076] At operation 640, a second collector may be applied over the ETL. While the second collector is illustrated as in ITO layer in FIG. 6, embodiments according to the present disclosure are not limited to this implementation. In other embodiments, the second collector may be, for example, but not limited to, thin metal multilayers, a silver nanowire network, or another material, formed on the ETL. The second collector may be a transparent collector.

[0077] The examples and embodiments described herein are for illustrative purposes only. Various modifications or changes in light thereof will be apparent to persons skilled in the art. These are to be included within the spirit and purview of this application, and the scope of the appended claims, which follow.