Hydrogen treatment for high performance chalcogenide thin film solar cells

Abstract

This disclosure generally relates to hydrogen enriched photovoltaic devices. In particular, the disclosure generally relates to hydrogen enriched photovoltaic devices comprising a light absorber layer of a semiconductor material, in particular chalcogenide semiconductor materials, for a thin film photovoltaic device. In addition, the present disclosure relates to methods of forming hydrogen enriched photovoltaic devices. More specifically, methods of increasing the hydrogen content of one or more layers within photovoltaic devices comprising a light absorber layer of a semiconductor material, in particular chalcogenide semiconductor materials, which may be used for a thin film photovoltaic device.

Description

HYDROGEN TREATMENT FOR HIGH PERFORMANCE CHALCOGENIDE THIN FILM SOLAR CELLSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority from Australian Provisional Patent Application No 2024903846 filed on 22 November 2024, the contents of which are incorporated herein by reference in their entirety.TECHNICAL FIELD

[0002] This disclosure generally relates to hydrogen enriched photovoltaic devices. In particular, the disclosure generally relates to hydrogen enriched photovoltaic devices comprising a light absorber layer of a semiconductor material for a thin film photovoltaic device. In addition, the present disclosure relates to methods of forming hydrogen enriched photovoltaic devices. More specifically, methods of increasing the hydrogen content of one or more layers within photovoltaic devices comprising a light absorber layer of a semiconductor material which may be used for a thin film photovoltaic device.BACKGROUND

[0003] Solar cells are photovoltaic devices that convert light into electrical energy. Solar cells generate clean, renewable energy and are increasingly being used to in a variety of markets, including residential rooftops, commercial rooftops, utility-scale photovoltaic projects, to meet the growing energy demand and to reduce reliance on fossil fuels.

[0004] Currently, crystalline silicon solar cells (both mono-crystalline and multicrystalline), are the dominant technologies in the market. Crystalline silicon solar cells must use a thick substrate (>100 pm) of silicon to absorb the sunlight since it has an indirect bandgap and low absorption coefficient. The use of a thick substrate also means that the crystalline silicon solar cells must use high quality material to provide long carrier lifetimes. Therefore, crystalline silicon solar cell technologies lead to increased costs.

[0005] Thin film photovoltaic devices comprising earth-abundant, non-toxic materials are considered as a promising option for next-generation photovoltaics. The thin film solar cells may be formed from amorphous, nanocrystalline, micromorph, microcrystalline, polycrystalline, or mono-crystalline materials and provide an opportunity to increase the material utilization since only thin films (<10 um) are generally required. Thin film photovoltaic devices may include a single absorber layer for converting light into electricity, or multiple absorber layers with tuned absorption spectra for converting light into electricity in a tandem configuration. The tandem configuration might be a two- terminal device, or a multi-terminal (e.g., four-terminal), device structure. The multi-terminal device structure might be comprised of one stack of layers on one substrate, or involve different stacks of layers on multiple stacked substrates. Unfortunately, the record efficiency of single-junction Cu2ZnSnS4 solar cells has stagnated at 11% since 2018, largely due to carriers recombining before being collected.

[0006] Therefore, it is desirable to provide alternative device architectures within increased efficient. It is also desirable to provide alternative methods for the producing photovoltaic devices with increased efficiency.SUMMARY

[0007] In first aspect of the present disclosure, there is provided a photovoltaic precursor device comprising: a substrate layer; a first conductive layer; optionally, an electron or hole transport layer; a light absorbing material layer; optionally, one or more buffer layers; and a second conductive layer; wherein:- the light absorbing material layer is disposed between the first conductive layer and the second conductive layer;- the first conductive layer is disposed between the substrate layer and the second conductive layer;- when present, the electron or hole transport layer is disposed between the and the first conductive layer and the light absorbing material layer;- when present, the one or more buffer layers are disposed between the light absorbing material layer and the second conductive layer; optionally when present, the one or more buffer layers have the opposite conductivity to the light absorbing material layer or are a dielectric material; wherein:- the light-absorbing material is at least one semiconductor compound; and at least one layer in the device is a hydrogen enriched layer.

[0008] In a second aspect of the present disclosure, there is provided a photovoltaic device comprising the photovoltaic precursor device of the first aspect.

[0009] In a third aspect of the present disclosure, there is provided a photovoltaic device comprising:a substrate layer; a first conductive layer; optionally, an electron or hole transport layer; a light absorbing material layer; optionally, one or more buffer layers; a second conductive layer; an optional metal contact; an anti-reflective layer, wherein:- the light absorbing material layer is disposed between the first conductive layer and the second conductive layer;- the first conductive layer and the second conductive layer are disposed between the substrate layer and the anti -reflective layer;- when present, the electron or hole transport layer is disposed between the and the first conductive layer and the light absorbing material layer;- when present, the one or more buffer layers are disposed between the light absorbing material layer and the second conductive layer; optionally when present, the one or more buffer layers have the opposite conductivity to the light absorbing material layer or are a dielectric material; wherein:- the light-absorbing material is a semiconductor compound; and at least one layer in the device is a hydrogen enriched layer.

[0010] In a fourth aspect of the present disclosure, there is provided a method of increasing the hydrogen content in an article comprising a light absorbing material, the method comprising contacting the article with a treatment gas comprising hydrogen, wherein the light-absorbing material is a semiconductor compound.

[0011] In a fifth aspect of the present disclosure, there is provided an article produced according to the method of the fourth aspect.

[0012] In one embodiment of the fifth aspect, the article is a photovoltaic precursor device according to the first aspect or a photovoltaic device according to the second or third aspect.

[0013] In some embodiments, the wherein the process further comprises thermally treating the article.

[0014] In some embodiments, in the method described herein, the article comprises:a substrate layer; a first conductive layer; optionally, an electron or hole transport layer; and a light absorbing material layer comprising the light absorbing material; wherein:- the first conductive layer is disposed between the substrate layer and the light absorbing material layer; and- when present, the electron or hole transport layer is disposed between the and the first conductive layer and the light absorbing material layer.

[0015] In another aspect of the present disclosure, there is provided an article produced according to the method as described herein.

[0016] In some embodiments, the article is a photovoltaic precursor device or photovoltaic device as described herein.

[0017] It will be appreciated that any one or more of the embodiments and examples described herein for the device may also apply to the articles, and methods described, and vice versa. Any embodiment herein shall be taken to apply mutatis mutandis to any other embodiment unless specifically stated. It will also be appreciated that other aspects, embodiments and examples of the devices, articles, and methods are described herein.BRIEF DESCRIPTION OF DRAWINGS

[0018] Preferred embodiments of the present disclosure will be further described and illustrated, by way of example only, with reference to the accompanying drawings in which:

[0019] Figure 1 : Cross-section SEM image of the CZTS device without anti-reflective layer;

[0020] Figure 2: ERDA measured hydrogen concentration in Ref and HT samples (Mo / CZTS / ZnSnO / ZnO structure);

[0021] Figure 3: APT element mappings for Zn, Sn, In, H, Na, and O in the HT device (Mo / CZTS / ZnSnO / ZnO / ITO structure) with ITO, ZnO, and CZTS layers labelled according to Zn, Sn, and In distributions and the ZnSnO layer is not distinguished owing to the limited thickness (around 10 nm);

[0022] Figure 4: ToF-SIMS elemental depth profiles of Ref and HT devices, showing Na, O (from CS2O+ signal for enhanced intensity), and Zn (for layer clarification);

[0023] Figure 5: KPFM images of (a) Ref and (b) HT devices with the red squares and arrows indicate the selected flat grains and directions for line scans (c,d) Line scans of contact potential difference (averaged over 20 pixels) of the (c) Ref and (d) HT samplesaccording to the indicated directions; (e,f) UPS spectra near the secondary electron cutoff region of Ref and HT films at (e) surface and in (f) bulk with the estimated depth of the bulk region beneath the surface is approximately 50 nm, according to the etching rate;

[0024] Figure 6: J-V curves and tabulated photovoltaic parameters of the most efficient Ref and HT devices;

[0025] Figure 7: Certificated current density -voltage results of the best performing HT cell at the National PV Industry Measurement and Testing Center;

[0026] Figure 8: Current density -voltage curves with tabulated parameters of the best performing HT device before and after 45 days of storage in an N2 desiccator without encapsulation;

[0027] Figure 9: Statistical analysis of performance of 10 cells for the Ref and HT samples with the box plot illustrates the median (centre line), mean value (dots), interquartile range from the 25thto the 75thpercentile (bottom to top of the box), the smallest and largest data points within 1.5 times the interquartile range from the box (whiskers), and outliers beyond the whiskers; and

[0028] Figure 10:Current density-voltage curves and tabulated parameters of Cu(In,Ga)S2 device before and after hydrogen treatment.DESCRIPTION OF EMBODIMENTS

[0029] The present disclosure describes the following various non-limiting embodiments, which relate to the present disclosure.Definitions

[0030] In the following description, reference is made, where needed, to any accompanying drawings which form a part hereof, and which is shown, by way of illustration, several embodiments. It is understood that other embodiments may be used, and structural changes may be made without departing from the scope of the present disclosure.

[0031] With regards to the definitions provided herein, unless stated otherwise, or implicit from context, the defined terms and phrases include the provided meanings. Unless explicitly stated otherwise, or apparent from context, the terms and phrases below do not exclude the meaning that the term or phrase has acquired by a person skilled in the relevant art. The definitions are provided to aid in describing particular embodiments, and are not intended to limit the claimed invention, because the scope of the invention is limited only by the claims. Furthermore, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular.

[0032] All publications discussed and / or referenced herein are incorporated herein in their entirety.

[0033] Throughout this disclosure, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e., one or more) of those steps, compositions of matter, groups of steps or groups of compositions of matter. Thus, as used herein, the singular forms “a”, “an” and “the” include plural aspects unless the context clearly dictates otherwise. For example, reference to “a” includes a single as well as two or more; reference to “an” includes a single as well as two or more; reference to “the” includes a single as well as two or more and so forth.

[0034] Those skilled in the art will appreciate that the disclosure herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications. The disclosure also includes all of the examples, steps, features, methods, processes, and compositions, referred to or indicated in this specification, individually or collectively, and any and all combinations or any two or more of said steps or features.

[0035] The term “and / or”, e.g., “X and / or Y” shall be understood to mean either “X and Y” or “X or Y” and shall be taken to provide explicit support for both meanings or for either meaning.

[0036] Unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to a “second” item does not require or preclude the existence of lower-numbered item (e.g., a “first” item) and / or a higher-numbered item (e.g., a “third” item).

[0037] As used herein, the phrase “at least one of’, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, or category. In other words, “at least one of’ means any combination of items or number of items may be used from the list, but not all of the items in the list may be required. For example, “at least one of item A, item B, and item C” may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, “at least one of item A, item B, and item C” may mean, for example and without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.

[0038] As used herein, the term “about”, unless stated to the contrary, typically refers to a range of up to + / - 10% of the designated value, and includes smaller ranges therein, for example + / - 5% or + / - 1% of the designated value.

[0039] It is to be appreciated that certain features that are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination.

[0040] Throughout the present specification, various aspects and components of the invention can be presented in a range format. The range format is included for convenience and should not be interpreted as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range, unless specifically indicated. For example, description of a range such as from 1 to 5 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 5, from 3 to 5 etc., as well as individual and partial numbers within the recited range, for example, 1, 2, 3, 4, 4.5, 4.75, and 5, unless where integers are required or implicit from context. This applies regardless of the breadth of the disclosed range. Where specific values are required, these will be indicated in the specification.

[0041] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0042] Throughout this specification, the term "consisting essentially of' is intended to exclude elements which would materially affect the properties of the claimed composition, method or process.

[0043] The terms "comprising", "comprise" and "comprises" herein are intended to be optionally substitutable with the terms "consisting essentially of', "consist essentially of', "consists essentially of, "consisting of, "consist of' and "consists of, respectively, in every instance.

[0044] Herein “weight %” may be abbreviated to as “wt%” or “wt.%”. The weight % may be w / w or w / v, unless specifically indicated or clear from context.

[0045] Herein, unless specifically defined a “device” may refer to a “photovoltaic precursor device” or a “photovoltaic device”.Device / Article configuration

[0046] Disclosed herein is a photovoltaic precursor device comprising: a substrate layer; a first conductive layer; optionally, an electron or hole transport layer;a light absorbing material layer; optionally, one or more buffer layers; and a second conductive layer; wherein:- the light absorbing material layer is disposed between the first conductive layer and the second conductive layer;- the first conductive layer is disposed between the substrate layer and the second conductive layer;- when present, the electron or hole transport layer is disposed between the and the first conductive layer and the light absorbing material layer;- when present, the one or more buffer layers are disposed between the light absorbing material layer and the second conductive layer; optionally when present, the one or more buffer layers have the opposite conductivity to the light absorbing material layer or are a dielectric material; wherein:- the light-absorbing material is at least one semiconductor compound; and at least one layer in the device is a hydrogen enriched layer.

[0047] Also disclosed herein is a photovoltaic device comprising the photovoltaic precursor device as described herein.

[0048] Also disclosed herein is a photovoltaic device comprising: a substrate layer; a first conductive layer; optionally, an electron or hole transport layer; a light absorbing material layer; optionally, one or more buffer layers; a second conductive layer; an optional metal contact; an anti-reflective layer, wherein:- the light absorbing material layer is disposed between the first conductive layer and the second conductive layer;- the first conductive layer and the second conductive layer are disposed between the substrate layer and the anti -reflective layer;- when present, the electron or hole transport layer is disposed between the and the first conductive layer and the light absorbing material layer;- when present, the one or more buffer layers are disposed between the light absorbing material layer and the second conductive layer; optionally when present, the one or more buffer layers have the opposite conductivity to the light absorbing material layer or are a dielectric material; wherein:- the light-absorbing material is a semiconductor compound; and at least one layer in the device is a hydrogen enriched layer.

[0049] According to some embodiments and examples, the inventors have discovered that devices disclosed herein display enhanced carrier collection. Without wishing to be bound by theory, the inventors opine that due to the presence of hydrogen, mainly incorporated within n-type layers, increasing the doping cotent, and at the light absorbing layer surface, oxygen and / or sodium diffuse from the bulk of the light absorbing layer to the surface of the light absorbing layer. Thus, according to some embodiments and examples, this advantageously diminishes the acceptor concentration at the surface of the light absorbing layer and / or increases the p-type doping in the bulk of the light absorbing layer, which can result in mitigation of Fermi-level pinning and / or facilitate carrier transport in the light absorbing layer. In other words, according to some embodiments and examples, devices of the present disclosure may exhibit reduced p-type doping near the surface of the light absorbing layer while exhibiting enhanced p-type doping in the deeper bulk region of the light absorbing layer. The reduced surface doping facilitates p- to-n type inversion and alleviates Fermi-level pinning, while the increased bulk doping may enhance carrier collection and overall device performance.

[0050] In one or more embodiments, a photovoltaic precursor device as described herein comprises one or more of the following components: (1) substrate; (2) first conductive layer; (3) optionally, an electron or hole transport layer; (4) a light absorbing material layer; (5) optionally, one or more buffer layers; (6) a second conductive layer; and (7) an anti -reflective layer. In one or more embodiments, one or more of components (1) to (7) may be arranged in a particular order.

[0051] In one or more embodiments, a photovoltaic device as described herein comprises one or more of the following components: (1) substrate; (2) first conductive layer; (3) optionally, an electron or hole transport layer; (4) a light absorbing material layer; (5) optionally, one or more buffer layers; (6) a second conductive layer; (7) an anti -reflective layer; and (8) a optionally a conductive metal electrode. In one or more embodiments, one or more of components (1) to (8) may be arranged in a particular order.

[0052] In one or more embodiments, the photovoltaic device comprises the following configuration: (1) substrate; (2) first conductive layer; (3) optionally, an electron or hole transport layer; (4) a light absorbing material layer; (5) optionally, one or more buffer layers; (6) a second conductive layer; (7) an anti-reflective layer; and (8) a optionally a conductive metal electrode.

[0053] In one or more embodiments, the light-absorbing material is a semiconductor compound.

[0054] In one or more embodiments, the light-absorbing material is a dielectric material.

[0055] In one or more embodiments, the light absorbing material layer is disposed between the first conductive layer and the second conductive layer.

[0056] In one or more embodiments, the first conductive layer and the second conductive layer are disposed between the substrate layer and the anti -reflective layer.

[0057] In one or more embodiments, when present, the electron or hole transport layer is disposed between the and the first conductive layer and the light absorbing material layer.

[0058] In one or more embodiments, when present, the one or more buffer layers are disposed between the light absorbing material layer and the second conductive layer.

[0059] In one or more embodiments, when present, the one or more buffer layers have the opposite conductivity to the light absorbing material layer or dielectric material.Substrate

[0060] It will be appreciated that for one or more of the devices described herein, the substrate may be a support, for example for supporting the superstrate configuration (2) to (8). In other words the substrate may support a photovoltaic stack.

[0061] In one or more embodiments, the substrate comprises a material selected from: glass, metal foil, and plastic. In one or more embodiments, the substrate is selected from glass and metal foil. In one or more embodiments, the substrate may be selected from soda-lime glass, low-iron glass, borosilicate glass, flexible glass, specialty glass for high temperature processing, stainless steel, carbon steel, aluminium, copper, titanium, molybdenum, polyimide, plastics, aluminosilicate glass, PET film, paper, cloth, cladded metal foils, and combinations thereof. In one or more embodiments, the substrate is or comprises soda-lime glass.

[0062] In one or more embodiments, the thickness of the substrate layer (in mm) is about, or greater than about: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4,1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4,3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5.0. In one or moreembodiments, the thickness of the substrate layer (in nm) is less than about: 5.0, 4.9, 4.8,4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8,2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1. In one or more embodiments, the thickness of the substrate layer (in mm) may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the thickness of the substrate layer (in mm) is between about 0.1 to about 5, between about 1.5 to about 3.5.First conductive layer

[0063] In one or more embodiments a first conductive layer is present on a device as described herein. In another embodiment, the first conductive layer is formed on the substrate.

[0064] In one or more embodiments, the first conductive layer is formed on the substrate. In one or more embodiments, the first conductive layer is formed on the substrate by sputtering.

[0065] In one or more embodiments, the first conductive layer comprises a material selected from: molybdenum (Mo), tungsten (W), aluminium (Al), fluorine-doped tin oxide (FTO), and indium tin oxide (ITO), and combinations thereof. In one or more embodiments, the first conductive layer comprises molybdenum (Mo).

[0066] In one or more embodiments, the thickness of the first conductive layer (in nm) is about, or greater than about: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, or 5000. In one or more embodiments, the thickness of the first conductive layer (in nm) is less than about: 5000, 4000, 3000, 2000, 1000, 900, 800, 700, 600, 500, 450, 400, 350, 300, 250, 200, 150, 100, 50, 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. In one or more embodiments, the thickness of the first conductive layer (in nm) may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the thickness of the first conductive layer (in nm) is between about 1 to about 5000, between about 10 to about 4000.Electron / hole transport layer

[0067] In one or more embodiments, one or more devices, as described herein, comprises an electron / hole transport layer. In one or more embodiments, one or more devices, as described herein, comprises an electron transport layer. In one or more embodiments, one or more devices, as described herein, comprises a hole transport layer. In another

[0068] In one or more embodiments, the electron / hole transport layer is disposed between the first conductive layer and the light absorbing material layer. In one or moreembodiments, the hole transport layer is disposed between the first conductive layer and the light absorbing material layer. In one or more embodiments, the hole transport layer is disposed between the first conductive layer and the light absorbing material layer.

[0069] In one or more embodiments, the electron transport layer comprises a material selected from: titanium dioxide (TiCE), zinc oxide (ZnO), indium tin oxide (ITO), cadmium sulfide (CdS), fullerene (Ceo), bathocuproine (BCP), phenyl-C61 -butyric acid methyl ester (PCBM), cesium carbonate (CS2CO3), aluminum-doped zinc oxide (AZO), magnesium oxide (MgO), lithium fluoride (LiF), nickel oxide (NiO), gallium oxide (GazCE), molybdenum trioxide (MoOs), molybdenum disulfide (M0S2), molybdenum diselenide (Mo S 62), cesium iodide (CsI), cesium fluoride (CsF), strontium titanate (SrTiOs), silicon dioxide (SiOz), hafnium oxide (HfCE), boron nitride (BN), tin dioxide (SnO2), or a mixture thereof.

[0070] In one or more embodiments, the thickness of the electron transport layer (in nm) is about, or greater than about: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000. In one or more embodiments, the thickness of the electron transport layer (in nm) is less than about: 1000, 900, 800, 700, 600, 500, 450, 400, 350, 300, 250, 200, 150, 100, 50, 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. In one or more embodiments, the thickness of the electron transport layer (in nm) may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the thickness of the electron transport layer (in nm) is between about 1 to about 1000, between about 10 to about 500.

[0071] In one or more embodiments, the hole transport layer comprises a material selected from: spiro-OMeTAD, poly(3,4-ethylenedioxythiophene) sulfonate (PEDOT), nickel oxide (NiO), copper iodide (Cui), copper thiocyanate (CuSCN), polytriarylamine (PTAA), poly(3 -hexylthiophene) (P3HT), molybdenum tri oxide (MoOs), cobalt complexes (e.g., Co(III) complexes), triphenylamine derivatives (TPA), polyTPD (poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine)), polyvinylcarbazole (PVK), tungsten trioxide (WO3), vanadium oxide (V2O5), poly(9,9-dioctylfluorene-co- bithiophene) (F8T2), 4,4'-bis(N-carbazolyl)-l,l'-biphenyl (CBP), benzotrithiophene (BTT) derivatives, tetraphenyldiamine (TPD), N,N'-Bis(3-methylphenyl)-N,N'- diphenylbenzidine (TPD), phenothiazine derivatives, or a mixture thereof.

[0072] In one or more embodiments, the thickness of the hole transport layer (in nm) is about, or greater than about: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000. In one or more embodiments, the thickness of the hole transport layer (in nm) is less than about: 1000, 900, 800, 700, 600, 500, 450, 400, 350, 300, 250, 200, 150, 100, 50, 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. In one or more embodiments, the thickness of the hole transport layer (in nm) may be ina range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the thickness of the electron transport layer (in nm) is between about 1 to about 1000, between about 10 to about 500.Light-absorbing material layer

[0073] In one or more embodiments, for a device as described herein, at least one light absorbing material is present. The person skilled in the art would understand that the light absorbing layer comprises the at least one light absorbing material. In one or more embodiments, the light-absorbing material layer comprises a light-absorbing material.

[0074] In one or more embodiments, the light-absorbing material is a semiconductor compound. In one or more embodiments, the semiconductor compound comprises a chalcogenide material. In one or more embodiments, the semiconductor compound consists essentially of a chalcogenide material.

[0075] The light absorbing layer may be formed by any suitable method known to the person skilled in the art. For example, the light absorbing layer may be formed by spin coating, doctor blade / slot-die coating a precursor solution comprising precursors of the light absorbing layer material and subsequently heat treating to form the light absorbing layer, inkjet printing / spray pyrolysis, electrochemical deposition, co-sputtering a precursor material to form the light-absorbing material layer.

[0076] In one or more embodiments, the light-absorbing material layer is formed on the first conductive material layer. In one or more embodiments, the light-absorbing material layer is formed by co-sputtering a precursor material to form a layer on the first conductive material layer.

[0077] In one or more embodiments, the light-absorbing material layer may be formed on the electron transport layer. In one or more embodiments, the light-absorbing material layer is formed by co-sputtering a precursor material to form a layer on the electron transport layer.

[0078] In one or more embodiments, the light-absorbing material may be formed on the hole transport layer. In one or more embodiments, the light-absorbing material layer is formed by co-sputtering a precursor material to form a layer on the hole transport layer.

[0079] In one or more embodiments, the thickness of the light-absorbing material layer (in nm) is about, or greater than about: 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, or 5000. In one or more embodiments, the thickness of the light-absorbing material layer (in nm) is less than about: 5000, 4000, 3000, 2000, 1000, 900, 800, 700, 600, 500, 450, 400, 350, 300, 250, 200, 150, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5. In one or more embodiments, the thickness of thelight-absorbing material layer (in nm) may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the thickness of the light-absorbing material layer (in nm) is between about 5 to about 5000, between about 200 to about 1000.

[0080] In one or more embodiments, the light-absorbing material layer comprises a light absorbing material selected from : tin sulfide (Sn-S), copper sulfide (Cu-S), zinc sulfide (Zn-S), indium sulfide (In-S), gallium sulfide (Ga-S), tin selenide (Sn-Se), copper selenide (Cu-Se), zinc selenide (Zn-Se), indium selenide (In-Se), gallium selenide (Ga- Se), copper tin sulfide (Cu-Sn-S), copper zinc sulfide (Cu-Zn-S), zinc tin sulfide (Zn-Sn- S), copper indium sulfide (Cu-In-S), copper gallium sulfide (Cu-Ga-S), copper indium gallium sulfide (Cu-In-Ga-S), copper tin selenide (Cu-Sn-Se), copper zinc selenide (Cu- Zn-Se), zinc tin selenide (Zn-Sn-Se), copper indium selenide (Cu-In-Se), copper gallium selenide (Cu-Ga-Se), copper indium gallium selenide (Cu-In-Ga-Se), antimony sulfide (Sb-S), antimony selenide (Sb-Se), antimony sulfide selenide (Sb-S-Se), copper indium gallium sulfide selenide (Cu-In-Ga-S-Se), copper zinc tin sulfide (Cu-Zn-Sn-S), copper zinc tin selenide (Cu-Zn-Sn-Se), copper zinc tin sulfide selenide (Cu-Zn-Sn-S-Se), cadmium telluride (Cd-Te), cadmium magnesium telluride (Cd-Mg-Te), cadmium zinc telluride (Cd-Zn-Te), cadmium selenide telluride (Cd-Se-Te), cadmium sulfide (Cd-S) and cadmium selenide (Cd-Se), or a mixture thereof. The use of hyphen (“-”, e.g., in Cu- S, or Cu-Sn-S) indicates that the formula encompasses all possible combinations of those elements, such as “Cu-S” encompasses CuS and CU2S. The stoichiometry of metals and chalcogens, for example between metal and metal, chalcogen and chalcogen, metal and chalcogen, can vary from a strictly molar ratio, such as 1 : 1 or 2: 1. Further, fractional stoichiometries, such as Cui.sS are also included.

[0081] In one or more embodiments, the light-absorbing material layer comprises a light absorbing material selected from CIGS-type I-III-VI multinary chalcogenide compounds or CZTS-type I-II-IV-VI multinary compounds.

[0082] In one or more embodiments, the light-absorbing material is selected from :CuSnS3, Sb2Se3, Sb2S3, Sb2(S,Se)3, AgBiS2, Cu3BiS3, CuBiS2, Cu(In,Ga)Se2(CIGSe), Cu(In,Ga)(S,Se)2(CIGSSe), Cu2ZnSnS4(CZTS), Cu2ZnSnSe4(CZTSe), Cu2ZnSn(S,Se)4(CZTSSe), Cu2O, TiO2, ZnO, SnO2, Cu2O, NiO, Fe2O3, WO3, MoO3, In2O3, Ga2O3, A12O3, V2Os, CeO2, ZrO2, or a mixture thereof.

[0083] In one or more embodiments, the light-absorbing material is selected from : Cu(Inx,Gai.x)(Sy,Sei.y)2wherein 0 ^ x ^ l, 0 ^ y ^ l or Cu2ZnSn(Sx,Sei-x)4wherein 0 x ^ 1. In one or more embodiments, the light absorbing material is selected from : Cu2MgSnS4, (Na,Cu)2ZnSnS4, (Li, Cu)2ZnSnS4, CuInSe2, CuInS2, CuGaSe2, CuGaS2, Cu(In,Ga)Se2, (Ag,Cu)(In,Ga)Se2, Cu(In,Ga)(S,Se)2, (Ag,Cu)(In,Ga)(S,Se)2, Cu(In,Ga)S2, (Ag,Cu)(In,Ga)S2, CdTe, CdZnTe, (Cd,Zn)(Te,Se), CdMgTe, Cu2ZnSnS4, Cu2ZnSnSe4, Cu2ZnSn(S,Se)4, (Ag,Cu)ZnSnS4, (Ag,Cu)ZnSnSe4, (Ag,Cu)ZnSn(S,Se)4, Cu2CdSnS4, Cu2CdSnSe4, Cu2CdSn(S,Se)4, Cu2(Cd,Zn)Sn(S,Se)4, Cu2(Cd,Zn)SnS4, Cu2(Cd,Zn)SnSe4, Cu2BaSnS4, Cu2BaSnSe4, Cu2BaSn(S,Se)4, Cu2Zn(Ge,Sn)S4, Cu2Zn(Ge,Sn)Se4, Cu2Zn(Ge,Sn)(S,Se)4, Cu2(Zn,Mn)SnS4, Cu2(Zn,Mn)SnSe4, Cu2(Zn,Mn)Sn(S,Se)4, Cu2(Zn,Fe)SnS4, Cu2(Zn,Fe)SnSe4, Cu2(Zn,Fe)Sn(S,Se)4, SnS, CuSnS3, Sb2Se3, Sb2S3, Sb2(S,Se)3, AgBiS2, Cu3BiS3, CuBiS2or a mixture thereof. In one or more embodiments, the light absorbing material is selected from: Cu(In,Ga)Se2(CIGSe), Cu(In,Ga)(S,Se)2(CIGSSe), Cu2ZnSnS4(CZTS), Cu2ZnSnSe4(CZTSe), Cu2ZnSn(S,Se)4(CZTSSe), or a mixture thereof.

[0084] In one or more embodiments, the light absorbing material is Cu2O, TiO2, ZnO, SnO2, Cu2O, NiO, Fe2O3, WO3, MoOs, In2O3, Ga2O3, A12O3, V2Os, CeO2, ZrO2, or a mixture thereof.

[0085] In one or more embodiments, the semiconductor compound is doped with an n- type dopant. In one or more embodiments, the n-type dopant is selected from: phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), and mixtures thereof.

[0086] In one or more embodiments, the semiconductor compound is doped with an p- type dopant. In one or more embodiments, the p-type dopant is selected from: boron (B), aluminum (Al), gallium (Ga), indium (In), zinc (Zn), magnesium (Mg), cadmium (Cd), copper (Cu), and mixtures thereof. In one or more embodiments, the p-type dopant is selected from zinc (Zn), copper (Cu), and mixtures thereof.One or more buffer layers

[0087] In one or more embodiments, a device, as described herein, comprises one or more buffer layers. In one or more embodiments, one or more buffer layer may be formed on the light-absorbing material layer.

[0088] In one or more embodiments, the one or more buffer layers comprise a semiconductor layer, such as an n-type semiconductor layer or a p-type semiconductor layer. In one or more embodiments, the one or more buffer layers comprise an electron transport material. In one or more embodiments, the one or more buffer layers comprise an hole transport material.

[0089] In one or more embodiments, the one or more buffer layers comprises a material selected from: aluminium oxide (AI2O3), cadmium sulfide (CdS), Zn(O,OH,S), indium sulfide (10283) zinc sulfide (ZnS), zinc cadmium sulfide (ZnCdS), zinc tin oxide ((ZnxSni-X)O), zinc magnesium oxide (ZnxMgi-xO), TiCh, Ceo, phenyl-Cei-butyric acid methyl ester, or mixtures thereof, wherein O ' x ' l .

[0090] In one or more embodiments, the thickness (in nm) of each of the one or more buffer layers is about, or greater than about: 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150. In one or more embodiments, the thickness (nm) of each of the one or more buffer layers is less than about 150, 140, 130, 120, 110, 100, 90, 80, 70, 60, 50, 40, 30, 20, 15, 10, or 5. In one or more embodiments, the thickness (in nm) of each of the one or more buffer layers may be in a range provided by any two of these upper and / or lower amounts. In one or more embodiments, the thickness (nm) of the each of the one or more buffer layers (nm) is between about 5 nm and about 150 nm.

[0091] In one or more embodiments, the device comprises a first buffer layer. In one or more embodiments, the first buffer layer comprises an electron transport material. In one or more embodiments, the first buffer layer comprises a material selected from: ZnSnO, CdS, MnS, ZnCdS, SnO, Zn(O,S), TiCh, Ceo, phenyl-Cei-butyric acid methyl ester, and mixtures thereof. In one or more embodiments, the first buffer layer comprises a material selected from: ZnSnO, CdS, and mixtures thereof.

[0092] In one or more embodiments, the thickness (nm) of the first buffer layer is about, or greater than about: 1, 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150. In one or more embodiments, the thickness (nm) of the first buffer layer is less than about 150, 140, 130, 120, 110, 100, 90, 80, 70, 60, 50, 40, 30, 20, 15, 10, 5, 4, 3, 2, or 1. In one or more embodiments, the thickness of the first buffer layer may be in a range provided by any two of these upper and / or lower amounts. In one or more embodiments, the thickness (nm) of the first buffer layer is between about 1 and about 150, or between about 5 to about 50.

[0093] In one or more embodiments, the device comprises a second buffer layer. In one or more embodiments, the second buffer layer is disposed between the first buffer layer and the second conductive layer. In one or more embodiments, the second buffer layer comprises an electron transport material. In one or more embodiments, the second buffer layer comprises a material selected from: ZnSnO, CdS, MnS, ZnCdS, SnO, Zn(O,S),TiCh, Ceo, phenyl-Cei-butyric acid methyl ester, and mixtures thereof. In one or more embodiments, the second buffer layer comprises ZnO. In one or more embodiments described herein, if the second buffer layer comprises ZnO, this layer may not be for the purpose of conducting, but instead may be an intrinsic ZnO (i-ZnO) which is a highly resistive layer used to prevent shunting.

[0094] In one or more embodiments, the thickness (nm) of the second buffer layer is about, or greater than about: 1, 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150. In one or more embodiments, the thickness (nm) of the second buffer layer is less than about 150, 140, 130, 120, 110, 100, 90, 80, 70, 60, 50, 40, 30, 20, 15, 10, 5, 4, 3, 2, or 1. In one or more embodiments, the thickness of the second buffer layer may be in a range provided by any two of these upper and / or lower amounts. In one or more embodiments, the thickness (nm) of the second buffer layer is between about 1 and about 150, or between about 20 to about 60.Second conductive layer

[0095] In one or more embodiments, a device, as described herein, comprises a second conductive layer.

[0096] In one or more embodiments, the second conductive layer is formed on the lightabsorbing layer.

[0097] In one or more embodiments, the second conductive layer is formed on the one or more buffer layers. In one or more embodiments, the second conductive layer is formed on the first buffer layer. In one or more embodiments, the second conductive layer is formed on the second buffer layer.In one or more embodiments, the second conductive layer comprises a transparent conductive layer. In one or more embodiments, the second conductive layer comprises a material selected from: zinc oxide (ZnO), indium tin oxide (ITO), boron-doped zinc oxide (BZO), aluminium-doped zinc oxide (AZO), gallium-doped zinc oxide (Ga-ZnO), zinc-doped indium oxide (IZO), and antimony tin oxide (ATO).

[0098] In one or more embodiments, the second conductive layer comprises a material selected from: zinc oxide (ZnO), aluminium-doped zinc oxide (AZO), and an indium tin oxide film (ITO) may be formed as the top electrode layer (or TCO) on the buffer layer.

[0099] In one or more embodiments, the thickness (in nm) of the second conductive layer is about, or greater than about: 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 180, 200, 220, 240, 280, 300, 320, 340, 380, 400, 420, 440, 480, 500, 520, 540, 580, or 600. In one or more embodiments, the thickness (in nm) of the second conductive layer is less than about: 600, 580, 540, 520, 500, 480, 440, 420, 400, 380, 360, 340, 320, 300, 280, 240, 220, 200, 180, 140, 120, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45,40, 35, 30, 25, 20, 15, 10, or 5. In one or more embodiments, the thickness (in nm) of the second conductive layer may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the thickness (in nm) of the second conductive layer is between about 5 to about 600, between about 100 to about 300.Metal contacts

[0100] In one or more embodiments, a device as described herein, comprises one or more metal contacts.

[0101] In one or more embodiments, the metal contact is formed on the second conductive layer. A number of metals may be used as metal contacts for different photovoltaic devices. In one or more embodiments, the metal contact comprises or is formed of: nickel (Ni), gold (Au), silver (Ag) and / or aluminium (Al). In one or more embodiments, the metal contact is Ni / Al / Ni.Anti -reflective layer

[0102] In one or more embodiments, a device as described herein comprises at least one ant-reflective layer.

[0103] In one or more embodiments, the anti -reflective layer may be formed on the second conductive layer. In one or more embodiments, the anti -reflective layer comprises a material selected from: magnesium fluoride (MgF2), lithium fluoride (LiF), silicon oxide (SiCh), silicon nitride (SisN^ and Niobium oxide (NbOx), or a mixture thereof. In one or more embodiments, the anti -reflective layer comprises MgF2.

[0104] In one or more embodiments, the thickness (nm) of the anti-reflective layer (in nm) is about, or greater than about: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150. In one or more embodiments, the thickness (nm) of the anti -reflective layer (in nm) is less than about : 150, 140, 130, 120, 110, 100, 90, 80, 70, 60, 50, 40, 30 or 20. In one or more embodiments, the thickness of the anti-reflective layer may be in a range provided by any two of these upper and / or lower amounts. In one or more embodiments, the thickness (nm) of the anti -reflective layer (in nm) is between about 10 and about 150, between about 50 and about 100.Passivating layers

[0105] In one or more embodiments, a device as described herein comprises one or more passivating layers.

[0106] In one or more embodiments, one or more layers in the device is coated with a passivating layer. In one or more embodiments, the passivating layer comprises a material selected from: silicon dioxide (SiCh), silicon nitride (SisN^, aluminum oxide (AI2O3), titanium dioxide (TiCh), hafnium oxide (HfCh), zinc oxide (ZnO), magnesium fluoride (MgF?), tantalum pentoxide (Ta20s), zirconium oxide (ZrCh), gallium oxide(Ga20s), graphene oxide, carbon nanotube (CNT) coatings, cadmium sulfide (CdS), lead iodide (PbL), barium titanate (BaTiCh), boron nitride (BN), molybdenum disulfide (M0S2), magnesium oxide (MgO), lithium fluoride (LiF), indium oxide (ImCh), caesium iodide (CsI), samarium oxide (SrmCf), lanthanum oxide (La2Os), vanadium oxide (V2O5), caesium fluoride (CsF), niobium oxide (Nb2Os), poly(3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT), methylammonium lead iodide (MAPbE), nickel oxide (NiOx), tungsten oxide (WO3), calcium fluoride (CaF2), aluminum fluoride (AIF3), and combinations thereof. In one or more embodiments, the passivating layer comprises a material selected aluminum oxide (AI2O3), lithium fluoride (LiF), and combinations thereof.

[0107] In one or more embodiments, the thickness of the passivating layer (in nm) is about, or greater than about: 0.1, 0.2, 0.3, 0.4 , 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100. In one or more embodiments, the thickness of the passivating layer (in nm) is less than about: 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1. In one or more embodiments, the thickness of the passivating layer (in nm) may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the thickness of the passivating layer (in nm) is between about 0.1 to about 100, between about 1 to about10.Exclusions

[0108] In one or more embodiments, one or more layers, or the device is substantially free of cadmium. In one or more embodiments, the device is substantially free of cadmium.

[0109] In one or more embodiments, one or more layers, or the device is substantially free of silicon. In one or more embodiments, the device is substantially free of silicon. In one or more embodiments, the light absorbing layer is substantially free of silicon. In one or more embodiments, the light-absorbing material is a semiconductor compound and is substantially free of silicon. In one or more embodiments, the semiconductor compound comprises a chalcogenide material and is substantially free of silicon. In one or more embodiments, the semiconductor compound substantially consists of a chalcogenide material and is substantially free of silicon.Hydrogen enriched

[0110] The term “hydrogen enriched” in the context of a “hydrogen enriched layer” will be understood to mean that the hydrogen content in the hydrogen enriched layer is increased relative to layers known in the art.

[0111] In one or more embodiments, at least one layer in the device is a hydrogen enriched layer. In one or more embodiments, the at least one hydrogen enriched layer is selected from one or more the light absorbing material layer, the one or more buffer layers, and the second conductive layer.

[0112] In one or more embodiments, at least a portion of at least one hydrogen enriched layer has a hydrogen content (in ppm) of at least: 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0113] In one or more embodiments, at least a portion of at least one hydrogen enriched layer has a hydrogen content (in ppm) of about, or greater than about: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, 90000, or 100000. In one or more embodiments, at least a portion of at least one hydrogen enriched layer has a hydrogen content (in ppm) of less than about: 100000, 90000, 80000, 70000, 60000, 50000, 40000, 30000, 20000, 10000, 9000, 8000, 7000, 6000, 5000, 4000, 3000, 2000, 1000, 900, 800, 700, 600, 500, 450, 400, 350, 300, 250, 200, 150, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. In one or more embodiments, the at least a portion of at least one hydrogen enriched layer has a hydrogen content (in ppm) may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, at least a portion of at least one hydrogen enriched layer has a hydrogen content (in ppm) is between about 1 to about 10000, between about 1 to about 100.

[0114] In one or more embodiments, the second conductive layer has a hydrogen content (in ppm) of about, or greater than about: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, or 10000. In one or more embodiments, the second conductive layer has a hydrogen content (in ppm) of less than about: 10000, 5000, 4000, 3000, 2000, 1000, 900, 800, 700, 600, 500, 450, 400, 350, 300, 250, 200, 150, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. In one or more embodiments, the second conductive layer has a hydrogen content (in ppm) which may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the second conductive layer has a hydrogen content (in ppm) is between about 1 to about 10000, between about 1 to about 100.

[0115] In one or more embodiments, the first buffer layer has a hydrogen content (in ppm) of about, or greater than about: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000,9000, or 10000. In one or more embodiments, the first buffer layer has a hydrogen content (in ppm) of less than about: 10000, 5000, 4000, 3000, 2000, 1000, 900, 800, 700, 600, 500, 450, 400, 350, 300, 250, 200, 150, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. In one or more embodiments, the first buffer layer has a hydrogen content (in ppm) which may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the first buffer layer has a hydrogen content (in ppm) is between about 1 to about 10000, between about 1 to about 100.

[0116] In one or more embodiments, the second buffer layer has a hydrogen content (in ppm) of about, or greater than about: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, or 10000. In one or more embodiments, the second buffer layer has a hydrogen content (in ppm) of less than about: 10000, 5000, 4000, 3000, 2000, 1000, 900, 800, 700, 600, 500, 450, 400, 350, 300, 250, 200, 150, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. In one or more embodiments, the second buffer layer has a hydrogen content (in ppm) which may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the second buffer layer has a hydrogen content (in ppm) is between about 1 to about 10000, between about 1 to about 100.

[0117] It will be understood that the surface of the light-absorbing material layer referred to in this paragraph is the surface of the light-absorbing layer which is proximate to the second conductive layer and does not refer to the surface of the light-absorbing layer which is closer to the substrate. In one or more embodiments, the surface of the light-absorbing material layer has a hydrogen content (in ppm) of about, or greater than about: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, or 10000. In one or more embodiments, the light-absorbing material layer has a hydrogen content (in ppm) of less than about: 10000, 5000, 4000, 3000, 2000, 1000, 900, 800, 700, 600, 500, 450, 400, 350, 300, 250, 200, 150, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. In one or more embodiments, the light-absorbing material layer has a hydrogen content (in ppm) which may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the lightabsorbing material layer has a hydrogen content (in ppm) is between about 1 to about 10000, between about 1 to about 100. The surface of the light absorbing may be defined by any suitable thickness and which can be considered the depth into the light absorbinglayer from the outer edge of said layer. In one or more embodiments, the thickness of the surface of the light-absorbing material layer (in nm) is about, or greater than about: 0.005, 0.01, 0.015, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, or 100. In one or more embodiments, the thickness of the surface of the light-absorbing material layer (in nm) is less than about: 100, 90, 80, 70, 60, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15, 0.14, 0.13, 0.12, 0.11, 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, 0.015, 0.01, 0.005. In one or more embodiments, the thickness of the surface of the light-absorbing material layer (in nm) may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the thickness of the surface of the light-absorbing material layer (in nm) is between about 0.005 to about 100.

[0118] In one or more embodiments, at least a portion of at least one hydrogen enriched layer has a hydrogen content (in ppm) which is increased relative to an equivalent layer which in a device or article which has not been subjected to a treatment method to increase the hydrogen content of at least a portion of at least one layer in the device or article by at least: 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0119] The concentration of hydrogen in one or more layers as described herein, may be measured by an appropriate technique known in the art. In one or more embodiments an appropriate recognised procedure or standard may be used. Examples of techniques that may be used include, but are not limited to: Atom Probe Tomography (APT) which measures atom ratios by field-evaporating atoms from a needle-shaped sample under a strong electric field, causing them to ionize and be projected toward a detector. The ions' time-of-flight (ToF) is used to determine their mass-to-charge ratio ( m I z m / z), identifying the element and isotopic composition.Method

[0120] Disclosed herein is a method of increasing the hydrogen content in an article comprising a light absorbing material. In some embodiments, the light absorbing material is a light absorbing material as described herein. The method comprising contacting the article with a treatment gas comprising hydrogen. In one or more embodiments, the lightabsorbing material is a semiconductor compound.

[0121] In one or more embodiments, the process further comprises thermally treating the article. In one or more embodiments, the thermally treating the article comprises exposing the article to a treatment temperature.

[0122] In one or more embodiments, the contacting the article with a treatment gas comprising hydrogen and the thermally treating the article occur simultaneously.

[0123] Sodium plays an essential role during the chalcogenide crystallization process and naturally diffuses from the widely used soda-lime glass substrate during crystallization. However, after crystallization, an uncontrolled sodium distribution in the final device can be detrimental, as sodium may occupy undesirable lattice sites and degrade device performance. The inventors of the present application have surprisingly discovered that thermally treating in a hydrogen atmosphere promotes a favorable redistribution of sodium from the bulk toward the absorber surface. According to some embodiments or examples, the methods described herein help reduce p-type doping near the surface while enhancing p-type doping in the deeper bulk region. The reduced surface doping facilitates p-to-n type inversion and alleviates Fermi-level pinning, while the increased bulk doping may enhance carrier collection and overall device performance.

[0124] The inventors of the present application have further surprisingly discovered that, according to some embodiments or examples, simultaneous contacting the device with hydrogen and thermally treating the device are advantageous as the heating may promote hydrogen diffusion into the device, enabling it to effectively regulate sodium redistribution. In contrast, heating alone provides limited control over sodium behavior, while introducing hydrogen without heating may produce no noticeable change in the device in a short period of time, for example 12 hours.

[0125] Also disclosed herein is an article produced according to a method as described herein. In one embodiment the article is a photovoltaic precursor device or a photovoltaic device as described herein.

[0126] In one or more embodiments of the present disclosure, there is provided a method of increasing the hydrogen content in an article comprising a light absorbing material, the method comprising contacting the article with a treatment gas comprising hydrogen, wherein the light-absorbing material is a semiconductor compound.

[0127] In one or more embodiments, the semiconductor compound comprises a chalcogenide material. In one or more embodiments, the semiconductor compound substantially consists of a chalcogenide material.

[0128] In one or more embodiments, the light absorbing layer is substantially free of silicon. In one or more embodiments, the light-absorbing material is a semiconductor compound and is substantially free of silicon. In one or more embodiments, the semiconductor compound comprises a chalcogenide material and is substantially free of silicon. In one or more embodiments, the semiconductor compound substantially consists of a chalcogenide material and is substantially free of silicon.

[0129] The inventors of the present application have surprisingly discovered that by contacting the article comprising the light absorbing layer to an external source of hydrogen it is possible to increase the hydrogen content in at least a region of the article.According to some embodiments or examples, this increase in hydrogen content in at least a region of the article is particularly advantageous when the article is a photovoltaic precursor device or a photovoltaic device as described herein and / or when the light absorbing layer is semiconductor compound comprising or substantially consists of a chalcogenide material as the inventors have discovered that the contacting with hydrogen may allow oxygen and / or sodium to diffuse from the bulk of the light absorbing layer to the surface. Thus, according to some embodiments and examples, this advantageously diminishes the acceptor concentration at the surface of the light absorbing layer and / or increases the p-type doping in the bulk of the light absorbing layer, which can result in mitigation of Fermi-level pinning and / or facilitate carrier transport in the light absorbing layer.Treatment gas

[0130] Hydrogen in the treatment gas may be obtained and / or generated from any suitable source known to the person skilled in the art. Examples of hydrogen sources include, but are not limited to: commercially available hydrogen; and / or hydrogen-containing gases or plasma precursors: such as NH3, H2O vapor, which can generate atomic or ionic hydrogen through plasma, thermal, or photolytic activation, including hydrogen isotopes may also be considered; and / or solid or thin-film hydrogen sources: such as SiN, a-Si, or AI2O3 containing -H or -OH groups, which can release hydrogen during annealing; and / or electrochemical or ion-based introduction: where hydrogen ions are incorporated via electrochemical hydrogenation or ion implantation followed by thermal activation; and / or chemical hydrogen storage materials: such as metal hydrides LiAlH4 or ammonia borane (NH3BH3), which can release hydrogen upon heating, hydrolysis, or catalytic decomposition.

[0131] In one or more embodiments, the treatment gas comprises hydrogen. In one or more embodiments, the treatment gas substantially consists of hydrogen.

[0132] In one or more embodiments, the treatment gas comprising hydrogen further comprises at least one other gas. In one or more embodiments, the at least one other gas in the treatment gas is an inert gas. In one or more embodiments, the inert gas is selected from nitrogen, helium, argon, and combinations thereof. In one or more embodiments, the inert gas is nitrogen. In one or more embodiments, the inert gas is argon.

[0133] In one or more embodiments, the hydrogen content in the treatment gas (in v / v%) is about, or greater than about: 0.1, 0.2, 0.3, 0.4 , 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4,5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, 99.5, 99.9. In some embodiments, the hydrogen content in the treatment gas (in v / v%) is less than about: 99.9, 99.5, 99, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1. In one or more embodiments, the hydrogen content in the treatment gas (in v / v%) may be in a range provided by any two of these upper and / or lower values. In one or more embodiments, the hydrogen content in the treatment gas (in v / v%) is between about 0.1 and about 99.9, between about 1 to about 50, between about 2 to about 15. In one or more embodiments, the hydrogen content in the treatment gas (in v / v%) is at least about 1.

[0134] In one or more embodiments, the inert gas content in the treatment gas (in v / v%) is about, or greater than about: 0.1, 0.2, 0.3, 0.4 , 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, 99.5, 99.9. In some embodiments, the inert gas content in the treatment gas (in v / v%) is less than about: 99.9, 99.5, 99, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1. In one or more embodiments, the inert gas content in the treatment gas (in v / v%) may be in a range provided by any two of these upper and / or lower values. In one or more embodiments, the inert gas content in the treatment gas (in v / v%) is between about 0.1 and about 99.9, between about 50 to about 99, between about 85 to about 98.Process conditions

[0135] In one or more embodiments, the treatment temperature (in °C) is about, or greater than about: 20, 30, 40, 50, 100, 150, 200, 250, 300, 350, or 400. In one or more embodiments, the treatment temperature (in °C) is less than about: 400, 350, 300, 250, 200, 150, 100, 50, 40, 30, or 20. In one or more embodiments, the treatment temperature (in °C) may be in a range provided by any two or more of the upper and / or lower amounts. In one or more embodiments the treatment temperature (in °C) is between about 20 and about 400, between about 100 to about 300, between about 150 and about 250, or between 180 to about 240.

[0136] In one or more embodiments, the article is heated to the treatment temperature at a rate (in °C / min) of about, or greater than about: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 13,3, 14, 15, 16, 17, 18, 19, or 20. In one or more embodiments, the article is heated to the treatment temperature at a rate (in °C / min) of less than about: 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. In one or more embodiments, the article is heated to the treatment temperature at a rate (in °C / min) which may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the article is heated to the treatment temperature at a rate (in °C / min) of between about 1 to about 20, or between about 5 to about 15.

[0137] In one or more embodiments, the article is heated for a period of time (minutes) of about, or greater than about: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 180, 240, 300, 360, 420, 480, 540, 600, 660, 720, 780, 840, 900, 960, 1020, 1080, 1140, 1200, 1260, 1320, 1380, or 1440 . In one or more embodiments, the article is heated for a period of time (minutes) of less than about: 1440, 1380, 1320, 1260, 1200, 1140, 1080, 1020, 960, 900, 840, 780, 720, 660, 600, 540, 480, 420, 360, 300, 240, 180, 120, 110, 100, 90, 80, 70, 60, 50, 40, 30, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. In one or more embodiments, the article is heated for a period of time (minutes) which may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the article is heated for a period of time (minutes) of between about 1 to about 1440, between about 1 to about 60, or between about 1 to about 10.

[0138] In one or more embodiments, the contacting the article with a treatment gas is performed for a period of time (minutes) of about, or greater than about: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 180, 240, 300, 360, 420, 480, 540, 600, 660, 720, 780, 840, 900, 960, 1020, 1080, 1140, 1200, 1260, 1320, 1380, or 1440 . In one or more embodiments, the contacting the article with a treatment gas is performed for a period of time (minutes) of less than about: 1440, 1380, 1320, 1260, 1200, 1140, 1080, 1020, 960, 900, 840, 780, 720, 660, 600, 540, 480, 420, 360, 300, 240, 180, 120, 110, 100, 90, 80, 70, 60, 50, 40, 30, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. In one or more embodiments, the contacting the article with a treatment gas is performed for a period of time (minutes) which may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the contacting the article with a treatment gas is performed for a period of time (minutes) of between about 1 to about 1440, between about 1 to about 60, or between about 1 to about 10.

[0139] In one or more embodiments, the treatment gas is gas stream. In one or more embodiments, the flow rate of the treatment gas (ml / min per cm2of cell cross section area) is about, or greater than about: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, or 1000. In one or more embodiments, the flow rate of the treatment gas (ml / min per cm2of cell cross section area) is less than about: 1000, 900, 800, 700, 600, 500, 450, 400, 350, 300, 250, 200, 150, 100, 50, 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. In one or more embodiments, the flow rate of the treatment gas (ml / min per cm2of cell cross section area) may be in a range provided by any two or more of these upper and / or lower amounts. In one or more embodiments, the flow rate of the treatment gas (ml / min per cm2of cell cross section area) of between about 1 to about 1000, between about 10 to about 500.EXAMPLE EMBODIMENTS

[0140] The present disclosure may be described by one or more of the following example embodiments:1. A photovoltaic precursor device comprising: a substrate layer; a first conductive layer; optionally, an electron or hole transport layer; a light absorbing material layer; optionally, one or more buffer layers; and a second conductive layer; wherein:- the light absorbing material layer is disposed between the first conductive layer and the second conductive layer;- the first conductive layer is disposed between the substrate layer and the second conductive layer;- when present, the electron or hole transport layer is disposed between the and the first conductive layer and the light absorbing material layer;- when present, the one or more buffer layers are disposed between the light absorbing material layer and the second conductive layer; wherein:- the light-absorbing material is at least one semiconductor compound; and at least one layer in the device is a hydrogen enriched layer.2. A photovoltaic device comprising the photovoltaic precursor device of claim 1.3. A photovoltaic device comprising: a substrate layer; a first conductive layer; optionally, an electron or hole transport layer; a light absorbing material layer; optionally, one or more buffer layers; a second conductive layer; an optional metal contact; an anti-reflective layer, wherein:- the light absorbing material layer is disposed between the first conductive layer and the second conductive layer;- the first conductive layer and the second conductive layer are disposed between the substrate layer and the anti -reflective layer;- when present, the electron or hole transport layer is disposed between the and the first conductive layer and the light absorbing material layer;- when present, the one or more buffer layers are disposed between the light absorbing material layer and the second conductive layer; optionally when present, the one or more buffer layers have the opposite conductivity to the light absorbing material layer or are a dielectric material; wherein:- the light-absorbing material is a semiconductor compound; and at least one layer in the device is a hydrogen enriched layer.4. The device of any one of the preceding embodiments, wherein the at least one hydrogen enriched layer is selected from one or more the light absorbing material layer, the one or more buffer layers, and the second conductive layer.5. The device of any one of the preceding embodiments, wherein at least a portion of at least one hydrogen enriched layer comprises at least 5 ppm of hydrogen.6. The device of any one of the preceding embodiments, wherein at least a portion of at least one hydrogen enriched layer comprises hydrogen in range of about 5 ppm to about 100,000 ppm.7. The device of any one of the preceding embodiments, wherein the at least one semiconductor compound comprises a chalcogenide compound.8. The device of any one of the preceding embodiments, wherein at least one semiconductor compound is selected from: Cu2ZnSn(S,Se)4, Cu(In,Ga)(S,Se)2, and Sb2(S,Se)3, or a mixture thereof.9. The device of any one of the preceding embodiments, comprising a first buffer layer.10. The device of any one of the preceding embodiments, wherein the first buffer layer comprises an electron transport material.11. The device of any one of the preceding embodiments, wherein the first buffer layer comprises ZnSnO, CdS, MnS, ZnCdS, SnO, Zn(O,S), TiCh, Ceo, phenyl-Cei- butyric acid methyl ester, or a mixture thereof.12. The device of any one of the preceding embodiments, comprising a second buffer layer.13. The device of any one of the preceding embodiments, wherein the second buffer layer comprises an electron transport material.14. The device of any one of the preceding embodiments, wherein the first buffer layer comprises ZnO, ZnSnO, CdS, MnS, ZnCdS, SnO, Zn(O,S), TiCh, Ceo, phenyl-Cei- butyric acid methyl ester, or a mixture thereof.15. The device of any one of the preceding embodiments, wherein the semiconductor compound is doped with an n-type dopant.16. The device of one of the preceding embodiments, wherein the n-type dopant is selected from phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), or a mixture thereof.17. The device of one of the preceding embodiments, wherein the semiconductor compound is doped with an p-type dopant.18. The device of one of the preceding embodiments, wherein the p-type dopant is selected from boron (B), aluminum (Al), gallium (Ga), indium (In), zinc (Zn), magnesium (Mg), cadmium (Cd), or a mixture thereof.19. The device of any one of the preceding embodiments, wherein one or more layers, or the device is substantially free of cadmium.20. The device of any one of the preceding embodiments, wherein one or more layers, or the device is substantially free of silicon.21. The device of any one of the preceding embodiments, wherein the substrate is selected from soda-lime glass or metal foil.22. The device of any one of the preceding embodiments, wherein the first conductive layer comprises a metal, a transparent conducting oxide, or a mixture thereof.23. The device of any one of the preceding embodiments, wherein the first conductive layer comprises Mo.24. The device of any one of the preceding embodiments, wherein the second conductive layer comprises a transparent conducting oxide, or a mixture thereof.25. The device of any one of the preceding embodiments, wherein the second conductive comprises ITO, AZO, BZO, IZO, or a mixture thereof.26. The device of any one of the preceding embodiments, wherein the second conductive comprises ITO.27. A method of increasing the hydrogen content in an article comprising a light absorbing material, the method comprising contacting the article with a treatment gas comprising hydrogen, wherein the light-absorbing material is a semiconductor compound.28. The method according to embodiment 27, wherein the process further comprises thermally treating the article.29. The method according to any embodiment 27 or embodiment 28 , wherein the contacting the article with a treatment gas comprising hydrogen and the thermally treating the article occur simultaneously.30. The method according to any one of embodiments 27 to 29, wherein the article comprises a plurality of layers and at least one layer comprises the light absorbing material.31. The method according to any one of embodiments 27 to 30, wherein the semiconductor compound comprises a chalcogenide compound.32. The method according to any one of embodiments 27 to 31, wherein the article comprises: a substrate layer; a first conductive layer; optionally, an electron or hole transport layer; and a light absorbing material layer comprising the light absorbing material; wherein:- the first conductive layer is disposed between the substrate layer and the light absorbing material layer; and- when present, the electron or hole transport layer is disposed between the and the first conductive layer and the light absorbing material layer.33. The method according to embodiment 32, wherein the article further comprises: a first buffer layer, wherein:- the light absorbing material layer is disposed between the first conductive layer and the first buffer layer; and optionally the first buffer layer has the opposite conductivity to the light absorbing material layer or are a dielectric material.34. The method according to embodiment 34, wherein the article further comprises: a second buffer layer, wherein:- the first buffer layer is disposed between the light absorbing material layer and the second buffer layer; andoptionally the second buffer layer has the opposite conductivity to the light absorbing material layer or dielectric material.35. The method according to embodiment 32 to 34, wherein the article further comprises: a second conductive layer, wherein:- the light absorbing material layer, and, if present, the first buffer layer and second buffer later, are disposed between the first conductive layer the second conductive layer.36. The method according to any one of embodiments 27 to 35, wherein the treatment gas comprising hydrogen further comprises at least one other gas.37. The method according of embodiments 36, wherein the at least one other gas in the treatment gas is an inert gas.38. The method according to embodiment 37, wherein the inert gas comprises: nitrogen, helium, argon, or a mixture thereof.39. The method according to embodiment 37 or embodiment 38, wherein the inert gas is argon.40. The method according to any one of embodiments 27 to 39, wherein the hydrogen content (in v / v%) in the treatment gas is at least about 1.41. The method according to any one of embodiments 27 to 40, wherein the hydrogen content in the treatment gas (% v / v) is between about 1 to about 50.42. The method according to any one of embodiments 27 to 41, wherein the hydrogen content in the treatment gas (% v / v) is between about 2 to about 15.43. The method according to any one of embodiments 37 to 42, wherein the inert gas content in the treatment gas (% v / v) is between about 50 to about 99.44. The method according to any one of embodiments 37 to 43, wherein the inert gas content in the treatment gas (% v / v) is between about 85 to about 98.45. The method according to any one of embodiments 28 to 44, wherein thermally treating the article comprises exposing the article to a treatment temperature in the range of about 50 °C to about 300 °C.46 The method according to any one of embodiments 27 to 45, wherein the flow rate of the treatment gas (ml / min per 0.224 cm2of cell) is between about 10 to about 100.47. The method according to any one of embodiments 27 to 46, wherein the flow rate of the treatment gas (ml / min per 0.224 cm2of cell) is between about 25 to about 75.48. The method according to any one of embodiments 27 to 47, wherein thermally treating the article comprises exposing the article to a treatment temperature (in °C) in the range of about 100 to about 300.49. The method according to any one of embodiments 27 to 48, wherein thermally treating the article comprises exposing the article to a treatment temperature (in °C) in the range of is between about 180 to about 240.50. The method according to any one of embodiments 27 to 49, wherein the article is heated to the treatment temperature at a rate (in °C / min) of between about 1 to about 20°C / min.51. The method according to any one of embodiments 27 to 50, wherein the article is heated to the treatment temperature at a rate (in °C / min) of between about 5 to about 15.52. The method according to any one of embodiments 27 to 51, wherein the contacting the article with a treatment gas is performed for a period of time (minutes) of between about 1 to about 1440.53. The method according to any one of embodiments 27 to 52, wherein the contacting the article with a treatment gas is performed for a period of time (minutes) of between about 1 to about 60.54. The method according to any one of embodiments 27 to 53, wherein the contacting the article with a treatment gas is performed for a period of time (min) of between about 1 to about 10.55. The method according to any one of embodiments 28 to 54, wherein the article is cooled after heat treatment.56. The method according to any one of embodiments 28 to 55, wherein the cooling after heat treatment at a rate (in °C / min) of between about 1 to about 20.57. The method according to any one of embodiments 27 to 56, wherein the process further comprises adding a coating to the article.58. The method according to embodiment 57, wherein the coating is an anti- reflective coating.59. The method according to any one of embodiments 27 to 58, wherein the article is a photovoltaic device according to any one of embodiments 1 to 26.61. An article produced according to the method of any one of embodiments 27 to60.62. The article according to embodiment 61, wherein the article is a photovoltaic precursor device or photovoltaic device according to any one of embodiments 1 to 26.EXAMPLESDevice manufacture

[0141] The CZTS device architecture had the following layered structure: Mo / CZTS / ZnSnO / ZnO / ITO / Ni-Al-Ni / MgF2.

[0142] The CZTS precursor layer was fabricated on soda-lime glass substrates coated with molybdenum, employing a sputtering system (AJA International, ATC-220). Through the co-sputtering of ZnS, SnS2, and Cu targets, with an Ar flow rate set at 15 seem and a pressure maintained at 1.5 mTorr, around 400 nm of CZTS precursor was deposited. The composition ratio of the precursor layer was controlled, achieving a Cu / Sn ratio of 1.5 and a Zn / Sn ratio of 1.0 through adjustment of the sputtering power for each target. The film was subsequently transferred into a quartz box containing S pellets and SnS powder within a rapid thermal processor (Annealsys, AS-One 100). With a heating rate of 0.5 °C / s, the sample underwent sulfurization annealing at 530 °C for 10 minutes.

[0143] Following the absorber fabrication, a ZnSnO buffer layer of 10 nm was deposited using atomic layer deposition (Cambridge Nanotech, Fiji G2 ALD). The substrate temperature was maintained at 150 °C throughout the deposition process. Then, 40 nm of ZnO and 210 nm of ITO were deposited by radiofrequency sputtering. The metal contact, consisting of 50 nm of Ni / 3 pm of Al / 50 nm of Ni, was applied using an E-beam evaporator (KJ Lesker, PVD-75).

[0144] The cell isolation was done by mechanical scribing, achieving a designed area of 0.224 cm2for each cell. Subsequently, hydrogen treatment was performed, details of which will be explained in the following section.

[0145] The device was transferred into a tube furnace for hydrogen treatment, conducted within a controlled atmosphere of 90% argon and 10% hydrogen. Before initiating the heating process, Ar and H2gas were purged into the tube furnace for 30 minutes with a total flow rate of 45 mL / min. The heating program was configured with a ramping-up rate of 10 °C / min, reaching a target temperature of 210 °C, and then maintained for 5 minutes.

[0146] The sample was then naturally cooled to room temperature and taken out. Lastly, the MgF2anti-reflective layer of 93 nm was thermally evaporated (Daedong high technologies, Solar-Dual Bridge).

[0147] A reference sample was coated without hydrogen treatment. A second set of reference samples were treated in a pure argon atmosphere using the same process as described above for the hydrogen treatment.

[0148] Throughout CZTS samples with the hydrogen treatment are denoted as HT, whereas the samples without hydrogen treatment are referred to as Ref, and samples with the argon treatment are referred to as ArgRef in the following discussion.Device characterisationDevice cross-section

[0149] Scanning electron microscope (SEM) was carried out using a Nova Nano 230, employing a 5 kV accelerating voltage and a 10 ps dwell time. A scanning electrode microscope (SEM) image of the device is shown in Figure 1.Hydrogen enrichment

[0150] Elastic recoil detection analysis (ERDA), an absolute technique commonly used to detect hydrogen, was used to characterise the hydrogen enrichment of layers in the device. Elastic recoil detection analysis (ERDA) was conducted on the Mo / CZTS / ZnSnO / ZnO sample using a monoenergetic He+beam of energy 2.8 MeV accelerated at a tandem ion accelerator (Pelletron accelerator at AFAiiR, ANU) is directed toward the samples at a typical incidence angle of the order of 75°. The content of hydrogen was then calculated assuming the density of CZTS is 4.56 g cm-3(corresponding to an atomic density of 2.79 x 1022atoms cm-3).

[0151] Figure 2 shows the hydrogen concentration of Ref and HT samples measured by elastic recoil detection analysis (ERDA). There is no ITO layer in this measurement, as the plural scattering effects will intensify with excessive sample thickness, limiting the detection sensitivity, especially for light elements like hydrogen. More hydrogen is located in the HT sample, mainly at the top region of the device compared with the bottom, confirming the introduction of hydrogen from the treatment gas. The hydrogen signal increased with a sharp cutoff near the surface in both samples, likely due to absorbed water during sample transfer. However, the HT sample exhibits obvious tails of the hydrogen signal extending from the surface to the bulk, which should be related to intrinsic hydrogen content

[0152] Atomic probe tomography (APT) was used to investigate the penetration depth of hydrogen in the HT sample. APT needle specimens were lifted out in a in a focused- ion beam / scanning electron microscope (Helios G4 PFIB UXe) and the tips direction were parallel to the substrates that was achieved by making a right triangle shape cantilever at the beginning, then the cantilever was rotated for 90 degrees twice using the manipulator and was welded to the post for further annular milling. APT experiment was performed in a Local Electrode Atom Probe (LEAP 4000X Si, CAMECA) at a pulse frequency of 200 kHz, a stage temperature of 50 K and a laser pulsing energy of 100 pj. APT data analysis was performed in the commercial software APSuite (Version 6.1.0.29,CAMECA). It was observed that hydrogen is mainly distributed in the n-type layers and a small amount in the surface area of the CZTS absorber, as shown in Figure 3. No hydrogen peak can be identified in the deeper absorber bulk regions in both samples.Oxygen and sodium diffusion

[0153] It was also observed that there is more Na at the CZTS surface in the HT sample, which may play a similar role to hydrogen since both Nai and Nacu (Na occupying Cu vacancy site with low formation energy) will moderate the p-type doping. Specifically, the Nai itself is positively charged, and the formation of neutral Nacu is accompanied by reducing the negatively charged Vcu. There also oxygen at the CZTS surface in addition to in the n-type layers, coinciding with the position of the Na signal.

[0154] Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was performed using a Cameca IMS 5fE7 system. The sample underwent sputtering using Cs+ ions with an energy of 1 keV over a 300 pm x 300 pm area, while the analysis region was confined to within 100 pm x 100 pm.

[0155] Figure 4 provides a direct comparison of the O and Na distribution for the for Ref and HT devices employing time-of-flight secondary ion mass spectrometry (ToF- SIMS). The HT sample demonstrates an increased Na intensity at the CZTS surface, which is consistent with APT results. Furthermore, the Na concentration within the CZTS bulk in the HT sample is lower than that in the Ref sample, indicating that the excess Na at the surface stems from Na out-diffusion from the deeper CZTS bulk area. The oxygen content in the bulk region (from around 600 s sputtering time) of the HT is obviously lower than that in the Ref sample, implying oxygen out-diffusion as well.

[0156] It is important to highlight that this Na diffusion pattern markedly differs from the typical device post-annealing behaviour observed where hydrogen is not involved. Although some reported similar increased Na density near the heterojunction interface, the corresponding devices also suffer from more Na in bulk when Na from the glass can diffuse freely. More Na diffusion from the substrate into the CZTS absorber, on the other hand, might be detrimental to device performance since the Na can either stay at interstitial positions or occupy benign Vcu sites, deteriorating bulk conductivity.

[0157] The doping profiles of Ref and HT devices are experimentally checked by crosssection amplitude-modulated Kelvin probe force microscopy (KPFM), as shown in as shown in Figure 5 (a,b). By line-scanning the contact potential difference of the absorber, as shown in Figure 5 (c,d), it is evident that the Ref sample demonstrates a relatively uniform doping distribution across the layer, while the HT sample exhibits a decreased p-type doping level near the surface compared with the deeper bulk.

[0158] Ultraviolet photoelectron spectroscopy (UPS) is further employed on the CZTS absorber to confirm the change in doping profiles without top layers, see Figure 5 (e,f). Ultraviolet photoelectron spectroscopy (UPS) was done in ESCALAB250Xi (Thermo Scientific) under a background vacuum better than 2E-9 millibar. The X-ray source was monochromatic Al K alpha (energy 1486.68 eV), and the spot size was 500 micrometres. The depth profiles were measured by mild etching the absorber film surface with an Ar ion beam (IkeV) at a rate of around 0.04 nm / sec. The HT sample displays a lower work function at the absorber surface than the Ref sample. Conversely, it presents a higher work function in the deeper bulk region.

[0159] Although the hydrogen treatment in this example just prior to addition of the anti -reflective layer, the UPS results suggest that this method is applicable to solar cells with different buffers and top layers, highlighting the transferability of the method described herein to a variety of photovoltaic device architectures.

[0160] In the Ref device, the high p-type doping at the absorber surface hinders the effective p-to-n type inversion at the interface, thus limiting band bending and quasi- Fermi-level splitting. On the contrary, the HT device should suffer less Voc loss at the interface due to reduced surface p-type doping, the carrier transport in the HT device will be facilitated since both the reduced p-type doping at the surface and increased doping in the bulk provide additional drift force for carrier transport, reducing recombination and thus enhancing short-circuit current density (J sc) and fill factor (FF).Device performance

[0161] The current density -voltage (J-V) curve was measured with a Keithley 2400 source meter and a solar simulator (ABET) under the illumination of the AMI.5 G spectrum with 100 mW cm -2 intensity. The light intensity was calibrated using a Si reference cell (Fraunhofer, WPVS). Temperature-dependent VOC was performed using the same system. A cryostat with liquid N2 was used to control the temperature from 100 to 310 K. The external quantum efficiency (EQE) was measured by a spectral response system (PV measurements, QEX10), which was calibrated using reference Si and Ge photodiodes (calibrated and certificated by the National Institute of Standards and Technology).

[0162] Figure 6 shows the current density-voltage (J-V) curves and PV parameters of the Ref and HT devices. All PV parameters are improved upon hydrogen treatment, contributing to 11.8% efficiency (Jscof 21.7 mA cm-2, Voc of 783.7 mV, and FF of 69.0%) and up to 11.4% certified efficiency (total area 0.2039 cm2, Figure 7).

[0163] Moreover, there is no distinguishable performance degradation for the HT device after storing in an N2 desiccator for 45 days without any encapsulation (Figure 8), confirming the device stability.

[0164] The statistic of device performance is presented in Figure 9, the average Voc increased from 709 mV to 780 mV, FF from 60.9% to 67.8%, Jsc from 21.3 mA cm'2to 21.7 mA cm'2and power conversion efficiency (PCE) from 9.2% to 11.5%. Jointly enhancing the Voc and FF of kesterite devices is considered challenging due to the inherent trade-offs widely observed. The concurrent improvement in all PV parameters suggests favourable carrier transport and collection in the HT device.Chalcopyrite semiconductor device

[0165] The hydrogen treatment was performed on the high bandgap chalcopyrite Cu(In,Ga)S2 (CIGS) device with a comparable structure (soda-lime glass / Mo / CIGS / ZnSnO / ZnO / ITO) to explore the universality of this technique. The CIGS fabrication process followed techniques known in the art with the inclusion of the hydrogen treatment step as described above. The treated CIGS device exhibits notable performance enhancement, especially the Voc, as shown in Figure 10.

[0166] The above results provide evidence that various embodiments of the photovoltaic devices and / or photovoltaic precursor devices disclosed herein, which comprise at least on hydrogen enriched layer, may be incorporated into photovoltaic devices with increased efficiency relative to photovoltaic devices known in the art. Further, the above results show that the hydrogen treatment method disclosed herein can advantageously be applied to devices comprising a variety of light absorbing materials, thereby providing a broad class of photovoltaic devices with increased efficiency relative to photovoltaic devices known in the art.

[0167] It will be appreciated by persons skilled in the art that numerous variations and / or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A photovoltaic precursor device comprising: a substrate layer; a first conductive layer; optionally, an electron or hole transport layer; a light absorbing material layer; optionally, one or more buffer layers; and a second conductive layer; wherein:- the light absorbing material layer is disposed between the first conductive layer and the second conductive layer;- the first conductive layer is disposed between the substrate layer and the second conductive layer;- when present, the electron or hole transport layer is disposed between the and the first conductive layer and the light absorbing material layer;- when present, the one or more buffer layers are disposed between the light absorbing material layer and the second conductive layer; wherein:- the light-absorbing material is at least one semiconductor compound; and at least one layer in the device is a hydrogen enriched layer.

2. A photovoltaic device comprising the photovoltaic precursor device of claim 1.

3. The device of claim 1 or claim 2, wherein the at least one semiconductor compound comprises a chalcogenide compound.

4. The device of any one of the preceding claims, wherein the at least one hydrogen enriched layer is selected from one or more the light absorbing material layer, the one or more buffer layers, and the second conductive layer.

5. The device of any one of the preceding claims, wherein at least a portion of at least one hydrogen enriched layer comprises hydrogen in range of about 5 ppm to about 100,000 ppm.

6. The device of any one of the preceding claims, wherein at least one semiconductor compound is selected from: Cu2ZnSn(S,Se)4, Cu(In,Ga)(S,Se)2, and Sb2(S,Se)3, or a mixture thereof.

7. The device of any one of the preceding claims, comprising a first buffer layer, optionally wherein the first buffer layer comprises an electron transport material furtheroptionally wherein the first buffer layer comprises ZnSnO, CdS, MnS, ZnCdS, SnO, Zn(O,S), TiCh, Ceo, phenyl-Cei-butyric acid methyl ester, or a mixture thereof.

8. The device of any one of the preceding claims, comprising a second buffer layer, optionally wherein the second buffer layer comprises an electron transport material, further optionally wherein the first buffer layer comprises ZnO, ZnSnO, CdS, MnS, ZnCdS, SnO, Zn(O,S), TiO2, Ceo, phenyl-Cei-butyric acid methyl ester, or a mixture thereof.

9. The device of any one of the preceding claims, wherein the semiconductor compound is doped with an n-type dopant, optionally wherein the n-type dopant is selected from phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), or a mixture thereof.

10. The device of one of the preceding claims, wherein the semiconductor compound is doped with an p-type dopant, optionally wherein the p-type dopant is selected from boron (B), aluminum (Al), gallium (Ga), indium (In), zinc (Zn), magnesium (Mg), cadmium (Cd), or a mixture thereof.

11. The device of any one of the preceding claims, wherein: one or more layers, or the device, is substantially free of cadmium; and / or wherein one or more layers, or the device is substantially free of silicon.

12. The device of any one of the preceding claims, wherein the first conductive layer comprises a metal, a transparent conducting oxide, or a mixture thereof, optionally wherein the first conductive layer comprises Mo.

13. The device of any one of the preceding claims, wherein the second conductive layer comprises a transparent conducting oxide, or a mixture thereof, optionally wherein the second conductive layer comprises ITO, AZO, BZO, IZO, or a mixture thereof, further optionally wherein the second conductive layer comprises ITO.

14. A method of increasing the hydrogen content in an article comprising a light absorbing material, the method comprising contacting the article with a treatment gas comprising hydrogen, wherein the light-absorbing material is a semiconductor compound.

15. The method according to claim 14, wherein the method further comprises thermally treating the article.

16. The method according to claim 15, wherein the contacting the article with a treatment gas comprising hydrogen and the thermally treating the article occur simultaneously.

17. The method according to claim 15 or claim 16, wherein thermally treating the article comprises exposing the article to a treatment temperature in the range of about 50°C to about 300 °C, optionally in the range of about 100 °C to about 300 °C, further optionally in the range of is between about 180 °C to about 240 °C.

18. The method according to any one of claims 15 to 17, wherein the article is heated to the treatment temperature at a rate (in °C / min) of between about 1 to about 20, optionally between about 5 to about 15.19 The method according to any one of claims 14 to 18, wherein the semiconductor compound comprises a chalcogenide compound.

20. The method according to any one of claims 14 to 19, wherein the article comprises: a substrate layer; a first conductive layer; optionally, an electron or hole transport layer; and a light absorbing material layer comprising the light absorbing material; wherein: the first conductive layer is disposed between the substrate layer and the light absorbing material layer; and when present, the electron or hole transport layer is disposed between the and the first conductive layer and the light absorbing material layer, optionally wherein the article further comprises: a first buffer layer, wherein: the light absorbing material layer is disposed between the first conductive layer and the first buffer layer; and optionally the first buffer layer has the opposite conductivity to the light absorbing material layer or are a dielectric material, further optionally wherein the article further comprises: a second buffer layer, wherein: the first buffer layer is disposed between the light absorbing material layer and the second buffer layer; and optionally the second buffer layer has the opposite conductivity to the light absorbing material layer or dielectric material; and / or a second conductive layer,wherein: the light absorbing material layer, and, if present, the first buffer layer and second buffer later, are disposed between the first conductive layer the second conductive layer.

21. The method according to any one of claims 14 to 20, wherein the treatment gas comprising hydrogen further comprises at least one other gas, optionally wherein the at least one other gas in the treatment gas is an inert gas, further optionally wherein the inert gas comprises: nitrogen, helium, argon, or a mixture thereof, further optionally wherein the inert gas is argon.

22. The method according to any one of claims 14 to 21, wherein the hydrogen content in the treatment gas (% v / v) is between about 1 to about 50, optionally wherein the hydrogen content in the treatment gas (% v / v) is between about 2 to about 15.

23. The method according to any one of claims 14 to 22, wherein the flow rate of the treatment gas (ml / min per 0.224 cm2of cell) is between about 10 to about 100, optionally between about 25 to about 75.

24. The method according to any one of claims 14 to 23, wherein the contacting the article with a treatment gas is performed for a period of time (minutes) of between about 1 to about 1440, optionally between about 1 to about 60, further optionally between about 1 to about 10.

25. The method according to any one of claims 14 to 24, wherein the process further comprises adding a coating to the article, optionally wherein the coating is an anti- reflective coating.

26. An article produced according to the method of any one of claims 14 to 25, optionally wherein the article is a photovoltaic precursor device or photovoltaic device according to any one of claims 1 to 13.

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