Methods for depositing perovskite materials

Abstract

The present invention discloses a method for depositing a perovskite material. The present invention provides a method for manufacturing a photovoltaic device, wherein the photovoltaic device includes a photosensitive region having a perovskite material layer, wherein the perovskite material layer is provided on a surface having a roughness average value (R) greater than or equal to 50 nm. a ) or root mean square roughness (R rms ) on a surface of a rough surface. The method comprises using vapor deposition to deposit a substantially continuous and conformal solid layer of one or more initial precursor compounds comprising the perovskite material, and subsequently treating the solid layer with one or more additional precursor compounds to form a substantially continuous and conformal solid layer of the perovskite material on the rough surface. A photovoltaic device comprising a photosensitive region having a layer of perovskite material disposed using the method is also provided.

Description

[0001] This application is a divisional application of the patent application with application number 201680034238.3 filed on December 12, 2017 and invention name “Method for depositing perovskite material”. Technical Field

[0002] The present invention relates to a method of depositing a conformal layer of a photosensitive perovskite material onto a rough or textured surface, and a photovoltaic device comprising a conformal layer of a photosensitive perovskite material disposed on a rough or textured surface. Background Art

[0003] Over the past four decades or so, there has been growing recognition of the need to replace fossil fuels with safer, sustainable energy sources. New energy supplies must also have a low environmental impact, be highly efficient, and be easy to use and inexpensive to produce. To this end, solar energy is considered one of the most promising technologies. However, the high cost of manufacturing devices that capture solar energy, including high material costs, has historically hindered its widespread use.

[0004] Each solid has its own unique energy band structure, which determines a wide range of electrical properties. Electrons can switch from one energy band to another, but each switch requires a specific minimum energy, and the amount of energy required will be different for different materials. Electrons obtain the energy required for the switch by absorbing phonons (heat) or photons (light). The term "band gap" refers to the energy difference range in a solid where no electronic state can exist, and usually means the energy difference (in electron volts) between the top of the valence band and the bottom of the conduction band. Under normal sunlight conditions, the efficiency of the materials used in photovoltaic devices (such as solar cells) is a function of the band gap used for the material. If the band gap is too high, most sunlight photons cannot be absorbed; if it is too low, most photons have much more energy than the energy required to excite electrons to cross the band gap, and the remainder will be wasted. The Shockley-Queisser limit refers to the theoretical maximum amount of electrical energy that can be extracted per photon of incident light and is approximately 1.34 eV. Much of the recent work in photovoltaic devices has focused on finding materials with a band gap as close as possible to this maximum.

[0005] One class of photovoltaic materials that has attracted considerable attention is hybrid organic-inorganic halide perovskites. This type of material forms an ABX3 crystal structure, which has been found to exhibit a good band gap, high absorption coefficient, and long diffusion length, making such compounds ideal as absorbers in photovoltaic devices. Early examples of hybrid organic-inorganic metal halide perovskite materials are reported by Kojima, A et al., 2009. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells, Journal of the American Chemical Society, 131(17), pp. 6050-6051, in which such perovskites were used as sensitizers in photoelectrochemical cells based on liquid electrolytes. Kojima et al. report that, although the perovskite absorber decays rapidly in this system and the performance of the cell degrades after only 10 minutes, the highest solar energy conversion efficiency (or power conversion efficiency, PCE) achieved is 3.8%.

[0006] Subsequently, the literature: Lee, M et al., 2012. Efficient hybrid solar cells based on meso-superstructured organometal halide perovskites, Science (New York, NY), 338 (6107), pp. 643-647 reported "meso-superstructure solar cells", in which the liquid electrolyte was replaced by a solid hole conductor (or hole transport material, HTM), spiro-MeOTAD. Lee et al. reported a significant increase in the conversion efficiency achieved, while also significantly improving the stability of the cell due to the avoidance of the use of liquid solvents. In the example described, CH3NH3Pbl3 perovskite nanoparticles act as a sensitizer within the photovoltaic cell, injecting electrons into the mesoscopic TiO2 support and holes into the solid-state HTM. Both TiO2 and HTM act as selective contacts, through which the charge carriers generated by the photoexcitation of the perovskite nanoparticles are extracted.

[0007] Further work described in WO2013 / 171517 discloses how the use of mixed-anion perovskites (rather than single-anion perovskites) as sensitizers / absorbers in photovoltaic devices can lead to more stable and efficient photovoltaic devices. Specifically, the document discloses that the devices exhibit negligible color bleaching during device fabrication, while also achieving full solar energy conversion efficiencies exceeding 10%. This finding highlights the superior stability of mixed-anion perovskites. In contrast, equivalent single-anion perovskites are relatively unstable, with bleaching occurring rapidly under ambient conditions when thin films are prepared from single halide perovskites.

[0008] Recently, WO2014 / 045021 describes a planar heterojunction (PHJ) photovoltaic device comprising a thin film of a photoactive perovskite absorber disposed between an n-type (electron transport) layer and a p-type (hole transport) layer. Unexpectedly, it was found that good device efficiency could be achieved using dense (i.e., without effective / open porosity) thin films of the photoactive perovskite, compared to the need for mesoporous composites, demonstrating that perovskite absorbers can function efficiently in simplified device architectures.

[0009] Recently, some research on the use of perovskites in photovoltaic devices has focused on the potential of these materials to improve the performance of conventional silicon-based solar cells by combining them with perovskite-based cells in a tandem / multi-junction arrangement. In this regard, a multi-junction photovoltaic device includes multiple individual sub-cells (i.e., each sub-cell has its own photoactive region) that are "stacked" on top of each other and together convert more of the solar spectrum into electricity, thereby increasing the overall efficiency of the device. To this end, each photoactive region of each sub-cell is selected such that the bandgap of the photoactive region ensures that it will efficiently absorb photons from a specific segment of the solar spectrum. This has two important advantages over conventional single-junction photovoltaic devices. First, the combination of multiple sub-cells / photoactive regions with different bandgaps ensures that a wider range of incident photons can be absorbed by the multi-junction device, and second, each sub-cell / photoactive region will be more efficient in extracting energy from photons within the relevant part of the spectrum. Specifically, the lowest bandgap of a multi-junction photovoltaic device will be lower than the lowest bandgap of a typical single-junction device, such that the multi-junction device will be able to absorb photons having less energy than those that can be absorbed by a single-junction device. Furthermore, for those photons that will be absorbed by both the multi-junction device and the single-junction device, the multi-junction device will absorb those photons more efficiently because having a bandgap closer to the photon energy reduces thermalization losses.

[0010] In a multi-junction device, the top sub-cell / photoactive region in the stack has the highest band gap, with the band gaps of the lower sub-cells / photoactive regions decreasing towards the bottom of the device. This arrangement maximizes the extraction of photon energy because the top sub-cell / photoactive region absorbs the most energetic photons while allowing photons with less energy to be transmitted. Each subsequent sub-cell / photoactive region then extracts energy from the photons closest to its band gap, minimizing thermalization losses. The bottom sub-cell / photoactive region then absorbs all remaining photons with energies above its band gap. When designing a multi-junction cell, it is therefore important to select sub-cells / photoactive regions with appropriate band gaps in order to optimize the harvesting of the solar spectrum. In this regard, for a tandem photovoltaic device comprising two subcells / photoactive regions (i.e., a top subcell / photoactive region and a bottom subcell / photoactive region), it has been shown that the bottom subcell / photoactive region should ideally have a band gap of approximately 1.1 eV, while the top subcell / photoactive region should ideally have a band gap of approximately 1.7 eV (Coutts, TJ, Emery, Ka & Scott Ward, J., 2002. Modeled performance of polycrystalline thin-film tandem solar cells, Progress in Photovoltaics: Research and Applications, 10(3), pp. 195-203).

[0011] Therefore, given that the band gap of these perovskite materials can be tuned from about 1.5 eV to over 2 eV by changing the halide composition of organometallic halide perovskites, there has been interest in developing hybrid organic-inorganic perovskite solar cells for use in tandem photovoltaic devices (Noh, JH et al., 2013. Chemical Management for Colorful, Efficient, and Stable Inorganic-Organic Hybrid Nanostructured Solar Cells, Nanoletters, 2, pp. 28-31). Specifically, by changing the halide composition, the band gap of organometallic halide perovskites can be tuned to about 1.7 eV, making them ideal for use as the top subcell in a tandem structure when combined with a crystalline silicon bottom subcell having a band gap of about 1.12 eV.

[0012] In this regard, Schneider, BW et al. (Schneider, BW et al., 2014. Pyramidal surface textures for light trapping and antireflection in perovskite-on-silicon tandem solar cells, Optics Express, 22 (S6), p. A1422) reported the modeling of a silicon-based perovskite tandem cell, wherein the model cell has a four-terminal mechanical stacking structure. Loper, P et al. (Loper, P et al., 2015. Organic-inorganic halide perovskite / crystalline silicon four-terminal tandem solar cells, Physical Chemistry Chemical Physics: PCCP, 17, p. 1619) reported the implementation of a four-terminal tandem solar cell consisting of a methylammonium lead triiodide (CH3NH3Pbl3) (i.e., an organic metal halide perovskite) top subcell mechanically stacked on a crystalline silicon heterojunction bottom subcell. Similarly, Bailie, C. et al. (Bailie, C. et al., 2015. Semi-transparent perovskite solar cells for tandems with silicon and CIGS, Energy Environ. Sci., pp. 1-28) reported mechanically stacked tandem solar cells consisting of methylammonium lead triiodide (CH3NH3Pbl3) top subcells on copper indium gallium diselenide (CIGS) or low-quality polycrystalline silicon bottom subcells. Filipic, M. et al. (Filipic, M. et al., 2015. CH3NH3Pbl3 perovskite / silicon tandem solar cells: characterization based optical simulations, Optics Express, 23(7), pp. 480-484) reported simulations of both mechanically stacked (four-terminal) tandem devices and monolithically integrated (two-terminal) tandem devices consisting of methylammonium lead triiodide (CH3NH3Pbl3) top subcells and crystalline silicon bottom subcells.Mailoa, JP et al. (Mailoa, JP et al., 2015. A 2-terminal perovskite / silicon multi-junction solar cell enabled by a silicon tunnel junction, Applied Physics Letters, 106(12), pp. 121105) subsequently reported the fabrication of a monolithic tandem solar cell consisting of a methylammonium lead triiodide (CH3NH3Pbl3) top subcell and a crystalline silicon bottom subcell.

[0013] In a mechanically stacked multi-junction photovoltaic device, the individual subcells are stacked on top of each other and each provided with their own individual electrical contacts, such that the individual subcells are connected in parallel and no current matching is required. This is in contrast to a monolithically integrated multi-junction photovoltaic device in which the individual subcells are electrically connected in series between a single pair of terminals, which results in the need for a recombination layer or tunnel junction and current matching between adjacent subcells. While mechanically stacked multi-junction photovoltaic devices do not require current matching between subcells, the additional size and cost of the additional contacts and substrate, as well as the lower practical efficiency limit, make the mechanical stacking structure less advantageous than the monolithically integrated structure.

[0014] When developing monolithically integrated silicon-based perovskite multi-junction photovoltaic devices, one of the most important considerations is the interface between the perovskite subcell and the adjacent crystalline silicon bottom subcell. In this regard, as described in the above-referenced references to Schneider, B.W. et al. and Filipic, M. et al., conventional commercial crystalline silicon solar cells feature textured surfaces designed to reduce reflections and increase optical path length, where these surface textures typically consist of randomly distributed pyramids (made by surface etching along the crystal planes) or regular inverted pyramids. Consequently, these textured surfaces pose significant challenges to the processing of monolithically integrated silicon-based perovskite photovoltaic devices, as the overall thickness of the perovskite subcell is typically similar to the roughness of the textured surface. For example, the surface roughness of conventional crystalline silicon solar cells is typically in the range of 500 nm to 10 μm, while the thickness of the perovskite cell is typically less than 1 μm. Specifically, although Schneider, B.W. et al. and Filipic, M. et al. attempted to model silicon-based perovskite tandem cells in which a conformal thin-film perovskite subcell is deposited onto the textured front surface of a silicon bottom subcell, neither document proposed a method for achieving such conformal deposition. Furthermore, Bailie, C. et al. state that the development of monolithic tandem cells incorporating a perovskite top cell will likely require planarizing the surface silicon bottom cell (i.e., reducing the surface roughness / removing any surface texture).

[0015] Therefore, to date, the only working examples of monolithically integrated silicon-based perovskite multi-junction photovoltaic devices utilize silicon bottom subcells with flat top surfaces to simplify the deposition of the perovskite, although this has been recognized to reduce the efficiency of the silicon bottom subcells (see the above-referenced literature by Mailoa, JP et al.). While this approach avoids the problems associated with the deposition of perovskite cells, it would require mechanical polishing of conventional crystalline silicon solar cells to form a flat surface, thereby increasing processing costs and reducing the efficiency of the silicon cells. Summary of the Invention

[0016] The inventors have developed a method for depositing a conformal layer of a photoactive perovskite material onto a rough or textured surface. Specifically, the inventors have developed a method for depositing a conformal and substantially continuous thin film of a photoactive perovskite material onto / over the textured top surface of a crystalline silicon solar cell, thereby providing an economical means for improving / enhancing the performance of market-leading crystalline silicon solar cells.

[0017] According to a first aspect, a method for manufacturing a photovoltaic device is provided, the photovoltaic device comprising a photosensitive region having a perovskite material layer, wherein the perovskite material layer is provided on a surface having a roughness average value (R a ) or root mean square roughness (R rms ). The method comprises using vapor deposition to deposit a substantially continuous and conformal solid layer of one or more initial precursor compounds comprising the perovskite material on the rough surface. The method further comprises subsequently treating the solid layer comprising the one or more initial precursor compounds with one or more other precursor compounds and thereby reacting the one or more initial precursor compounds and the one or more other precursor compounds to form a substantially continuous and conformal solid layer of the perovskite material on the rough surface.

[0018] The step of treating the solid layer comprising the one or more initial precursor compounds may comprise treating the solid layer comprising the one or more initial precursor compounds with a solution comprising the one or more further precursor compounds using solution deposition. Alternatively, the step of treating the solid layer comprising the one or more initial precursor compounds may comprise treating the solid layer comprising the one or more initial precursor compounds with the one or more further precursor compounds using vapor deposition.

[0019] The perovskite material layer may include a thin film of the perovskite material. The thickness of the thin film of the perovskite material is preferably 50 nm to 2 μm, more preferably 100 nm to 1000 nm, and even more preferably 200 nm to 700 nm.

[0020] The surface may have a roughness average value (R a ) or root mean square roughness (R rms ), and more preferably in the range of 1 μm to 10 μm.

[0021] The perovskite material preferably comprises a perovskite having the following general formula:

[0022] [A][B][X]3(I)

[0023] wherein [A] is one or more monovalent cations, [B] is one or more divalent inorganic cations, and [X] is one or more halide anions.

[0024] [X] may contain one or more halide anions selected from fluoride, chloride, bromide, and iodide, and is preferably selected from chloride, bromide, and iodide, and is more preferably selected from bromide and iodide. [X] may contain two different halide anions selected from fluoride, chloride, bromide, and iodide, and is preferably selected from chloride, bromide, and iodide, and is more preferably bromide and iodide.

[0025] [A] may contain a compound selected from methylammonium (CH3NH3 + ), formamidine (HC(NH)2)2 + ) and ethylammonium (CH3CH2NH3 + ) one or more organic cations. [A] may comprise one or more organic cations selected from Cs + , Rb + 、Cu + 、Pd + , Pt + 、Ag + 、Au + , Rh + and Ru + , and is preferably selected from Cs + and Rb + One or more inorganic cations, and more preferably Cs + .

[0026] [B] may contain Pb 2+ and Sn 2+ at least one divalent inorganic cation, and more preferably comprises Pb 2+ .

[0027] Each of the one or more initial precursor compounds comprises one of the one or more divalent inorganic cations [B], and each of the one or more further precursor compounds comprises one of the one or more monovalent cations [A].

[0028] Each of the one or more initial precursor compounds and each of the one or more further precursor compounds further comprises one of the one or more halide anions [X].

[0029] In the case where [A] comprises one or more inorganic cations, each of the one or more initial precursor compounds may then comprise one of the one or more monovalent inorganic cations [A], and each of the one or more further precursor compounds may then comprise one of the one or more divalent inorganic cations [B].

[0030] Each of the one or more initial precursor compounds and each of the one or more further precursor compounds may further comprise one of the one or more halide anions [X].

[0031] The step of using vapor deposition to deposit a substantially continuous and conformal solid layer comprising the one or more initial precursor compounds of the perovskite material on the rough surface may include using vapor deposition to deposit a substantially continuous and conformal solid layer comprising an inorganic material onto the rough surface, and subsequently treating the solid layer of inorganic material with a gas of a halide X and thereby reacting the inorganic material and the halide to form a substantially continuous and conformal solid layer comprising the one or more initial precursor compounds on the rough surface.

[0032] Each of the one or more initial precursor compounds may comprise one of the one or more divalent inorganic cations [B], and the inorganic material comprises an inorganic material that forms the one or more divalent inorganic cations [B]. The one or more monovalent cations [A] may comprise one or more inorganic cations, and each of the one or more initial precursor compounds may comprise one of the one or more monovalent inorganic cations, and the inorganic material comprises an inorganic material that forms the one or more monovalent inorganic cations.

[0033] The band gap of the perovskite material may be 1.10 eV to 2.30 eV, and preferably 1.65 eV to 1.75 eV.

[0034] The photovoltaic device may have a multi-junction structure including a first subcell disposed on a second subcell, the first subcell including a photoactive region including a perovskite material.

[0035] The adjacent surface of the second subcell may have an average roughness (R a ) or root mean square roughness (R rms ), and the rough surface on which the perovskite material layer is disposed may be a surface conforming to the rough surface of the second sub-cell.

[0036] The rough surface of the second sub-cell may include a surface of the second sub-cell or a surface within the second sub-cell provided with a surface texture, and the surface texture preferably includes one of a pyramid and an inverted pyramid.

[0037] The surface on which the solid layer of perovskite material is disposed may be any one of an adjacent surface of the second sub-cell and an adjacent surface of a layer disposed between the solid layer of perovskite material and the second sub-cell and conforming to the rough surface of the second sub-cell. The solid layer of perovskite material may be separated from the second sub-cell by one or more layers, each of which substantially conforms to the rough surface of the second sub-cell.

[0038] According to a second aspect, there is provided a multijunction photovoltaic device comprising a first subcell disposed on a second subcell, the first subcell comprising the photoactive region comprising a solid layer of perovskite material, wherein a surface of the second subcell adjacent to the first subcell has a roughness average value (R a ) or root mean square roughness (R rms ), and the solid layer of perovskite material is disposed as a substantially continuous and conformal layer on a surface that conforms to the rough surface of the second sub-cell.

[0039] The rough surface of the second subcell adjacent to the first subcell may include a surface within the second subcell provided with a surface texture, and the surface texture preferably includes one of a pyramid and an inverted pyramid.

[0040] The surface on which the solid layer of perovskite material is disposed may be any one of an adjacent surface of the second subcell and an adjacent surface of a layer disposed between the solid layer of perovskite material and the second subcell and conforming to the rough surface of the second subcell.

[0041] The solid layer of perovskite material may be separated from the second subcell by one or more layers that each substantially conform to the rough surface of the second subcell. The one or more layers that separate the solid layer of perovskite material from the second subcell and each substantially conform to the rough surface of the second subcell may include any one of the charge transport layer of the photosensitive region of the first subcell and one or more interconnect layers disposed between and connecting the first and second subcells.

[0042] The surface on which the solid layer of perovskite material is disposed may include an adjacent surface of a charge transport layer of the photosensitive region of the first subcell and an adjacent surface of an interconnect layer disposed between and connecting the first subcell and the second subcell.

[0043] The solid layer of the perovskite material may include a thin film of the perovskite material. The thickness of the thin film of the perovskite material is preferably 50 nm to 2 μm, more preferably 100 nm to 1000 nm, and even more preferably 200 nm to 700 nm.

[0044] The rough surface of the second subcell may have a roughness average value (R a ) or root mean square roughness (R rms ).

[0045] The second subcell may comprise any of a second perovskite material, crystalline silicon, CdTe, CuZnSnSSe, CuZnSnS, or CuInGaSe (CIGS). The second subcell may comprise a crystalline silicon subcell, and more preferably, the crystalline silicon subcell comprises a silicon heterojunction (SHJ), and even more preferably, the crystalline silicon subcell comprises an amorphous silicon:crystalline silicon heterojunction.

[0046] The perovskite material may comprise a perovskite having the formula:

[0047] [A][B][X]3 (I)

[0048] wherein [A] is one or more monovalent cations, [B] is one or more divalent inorganic cations, and [X] is one or more halide anions.

[0049] [X] may contain one or more halide anions selected from fluoride, chloride, bromide, and iodide, and is preferably selected from chloride, bromide, and iodide, and is more preferably selected from bromide and iodide. [X] may contain two different halide anions selected from fluoride, chloride, bromide, and iodide, and is preferably selected from chloride, bromide, and iodide, and is more preferably bromide and iodide.

[0050] [A] may contain a compound selected from methylammonium (CH3NH3 + ) and formamidine (HC(NH)2)2 + ) one or more organic cations. [A] may comprise one or more organic cations selected from Cs + , Rb + 、Cu + 、Pd + , Pt + 、Ag + 、Au + , Rh + and Ru + , and is preferably selected from Cs + and Rb + One or more inorganic cations, and more preferably Cs + .

[0051] [B] may contain Pb 2+ and Sn 2+ at least one divalent inorganic cation, and more preferably comprises Pb 2+ .

[0052] The band gap of the perovskite material may be 1.10 eV to 2.30 eV, and preferably 1.65 eV to 1.75 eV.

[0053] The perovskite material is preferably configured to act as a light absorber / photosensitizer within the photosensitive region.

[0054] The photosensitive region may include an n-type region having at least one n-type layer, a p-type region having at least one p-type layer, and a layer of perovskite material disposed between the n-type region and the p-type region. The charge transport material layer may then include either the n-type layer of the n-type region or the p-type layer of the p-type region.

[0055] The photosensitive region may include a layer of the perovskite material without open porosity. The layer of the perovskite material may form a planar heterojunction with one or both of the n-type region and the p-type region.

[0056] The photovoltaic device may further include a first electrode and a second electrode, wherein the first sub-cell and the second sub-cell are disposed between the first electrode and the second electrode. The first electrode may contact the p-type region of the first sub-cell, and the second electrode may contact the second sub-cell. The first electrode preferably comprises a transparent or semi-transparent conductive material, and the second electrode preferably comprises a metal. Alternatively, the first electrode may contact the n-type region of the first sub-cell, and the second electrode may contact the second sub-cell. The first electrode preferably comprises a transparent or semi-transparent conductive material, and the second electrode comprises a metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

[0058] Figure 1 A single-junction photovoltaic device is schematically shown;

[0059] Figure 2a Schematic illustration of a perovskite-based single-junction photovoltaic device with a regular structure;

[0060] Figure 2b Schematic illustration of a perovskite-based single-junction photovoltaic device with an inverted structure;

[0061] Figure 3a Schematically illustrates an exemplary perovskite-based single-junction photovoltaic device with an extremely thin absorber (ETA) cell architecture;

[0062] Figure 3b Schematically illustrates an exemplary perovskite-based single-junction photovoltaic device with a medium-scale superstructure solar cell (MSSC) architecture;

[0063] Figure 3c Schematically illustrates an exemplary perovskite-based single-junction photovoltaic device with a flat / planar junction architecture;

[0064] Figure 4 A multi-junction photovoltaic device is schematically shown;

[0065] Figure 5a Schematic illustration of a perovskite-based multijunction photovoltaic device with a regular structure;

[0066] Figure 5b Schematic illustration of a perovskite-based multi-junction photovoltaic device with an inverted structure;

[0067] Figure 6a Schematic illustration of an exemplary perovskite-based tandem photovoltaic device with a crystalline silicon bottom subcell;

[0068] Figure 6b Schematic illustration of an exemplary perovskite-based tandem photovoltaic device with a CIGS, CIS, or CZTSSe bottom subcell;

[0069] Figure 6c schematically illustrates an exemplary perovskite-based tandem photovoltaic device having a bottom subcell comprising a second photoactive / light-absorbing perovskite material;

[0070] Figure 7a Schematic illustration of a conformal layer of perovskite material deposited on the roughened top surface of the lower subcell of a multi-junction photovoltaic device;

[0071] Figure 7b Schematic illustration of a conformal layer of perovskite material deposited on the roughened top surface of the lower subcell of a multi-junction photovoltaic device;

[0072] Figure 8a schematically illustrates an exemplary embodiment of a method of manufacturing a photovoltaic device as described herein;

[0073] Figure 8b schematically illustrates an alternative exemplary embodiment of a method of manufacturing a photovoltaic device as described herein;

[0074] Figure 9 is an SEM image of a layer of perovskite material deposited on a textured silicon substrate using conventional methods; and

[0075] Figure 10 is an SEM image of a layer of perovskite material deposited on a textured silicon substrate using the method described herein. DETAILED DESCRIPTION

[0076] definition

[0077] As used herein, the term "photosensitive" refers to a region, layer, or material that is capable of photoelectrically responding to light. A photosensitive region, layer, or material is therefore capable of absorbing energy carried by photons in light, which subsequently results in the generation of electricity (e.g., by generating electron-hole pairs or excitons).

[0078] As used herein, the term "conformal" refers to an object that is substantially identical in form or shape to another object. Thus, as used herein, a "conformal layer" refers to a layer of material that conforms to the contours of the surface on which it is formed. In other words, the morphology of the layer is such that the thickness of the layer is approximately constant across most of the interface between the layer and the surface on which it is formed.

[0079] The term "perovskite" as used herein refers to a material having a three-dimensional crystal structure related to the structure of CaTiO3 or a material comprising a layer of material having a structure related to the structure of CaTiO3. The structure of CaTiO3 can be represented by the formula ABX3, where A and B are cations of different sizes, and X is an anion. In the unit cell, the A cations are at (0, 0, 0), the B cations are at (1 / 2, 1 / 2, 1 / 2), and the X anions are at (1 / 2, 1 / 2, 0). The A cations are generally larger than the B cations. It will be understood by those skilled in the art that as A, B, and X vary, the different ion sizes may cause the structure of the perovskite material to distort away from the structure adopted by CaTiO3 to a distorted structure with less symmetry. If the material includes a layer having a structure related to the structure of CaTiO3, the symmetry will also be lower. Materials comprising a layer of perovskite material are well known. For example, a perovskite material made of K2N i The structure of the F4-type structured material includes a layer of perovskite material. Those skilled in the art will appreciate that the perovskite material can be represented by the formula [A][B][X]3, where [A] is at least one cation, [B] is at least one cation, and [X] is at least one anion. When the perovskite contains more than one A cation, different A cations can be distributed in an ordered or disordered manner at the A sites. When the perovskite contains more than one B cation, different B cations can be distributed in an ordered or disordered manner at the B sites. When the perovskite contains more than one X anion, different X cations can be distributed in an ordered or disordered manner at the X sites. The symmetry of a perovskite containing more than one A cation, more than one B cation, or more than one X anion will generally be lower than the symmetry of CaTiO3.

[0080] As mentioned in the preceding paragraph, the term "perovskite," as used herein, refers to either (a) a material having a three-dimensional crystal structure related to that of CaTiO3 or (b) a material comprising a layer of material, wherein the layer has a structure related to that of CaTiO3. Although both classes of perovskites can be used in devices according to the present invention, in some cases it is preferred to use the first class of perovskites (a), i.e., perovskites having a three-dimensional (3D) crystal structure. Such perovskites typically comprise a 3D network of perovskite unit cells without any separation between the layers. On the other hand, the second class of perovskites (b) comprises perovskites having a two-dimensional (2D) layered structure. Perovskites having a 2D layered structure can comprise layers of perovskite unit cells separated by (intercalated) molecules; an example of such a 2D layered perovskite is [2-(1-cyclohexenyl)ethylammonium]2PbBr4. 2D layered perovskites tend to have high exciton binding energies, which favors the generation of bound electron-hole pairs (excitons) rather than free charge carriers upon photoexcitation. The movement of bound electron-hole pairs may not be sufficient to reach the p-type or n-type contacts where they can then transfer (ionize) and generate free charges. Therefore, in order to generate free charges, the exciton binding energy must be overcome, which means that the charge generation process consumes energy and leads to a voltage drop and reduced efficiency in the photovoltaic cell. In contrast, perovskites with a 3D crystal structure tend to have a lower exciton binding energy (similar to thermal energy) and can therefore generate free carriers directly after photoexcitation. Therefore, the perovskite semiconductor used in the device and process of the present invention is preferably a first type perovskite (a), i.e. a perovskite with a three-dimensional crystal structure. This is particularly preferred when the optoelectronic device is a photovoltaic device.

[0081] The perovskite material employed in the present invention is a material that is capable of absorbing light and thereby generating free charge carriers. Thus, the perovskite employed is a light-absorbing perovskite material. However, the skilled person will appreciate that the perovskite material may also be a perovskite material that is capable of emitting light by accepting charges (both electrons and holes) that subsequently recombine and emit light. Thus, the perovskite employed may be a light-emitting perovskite.

[0082] As will be appreciated by those skilled in the art, the perovskite material employed in the present invention may be a perovskite that acts as an n-type electron transport semiconductor when light-doped. Alternatively, it may be a perovskite that acts as a p-type hole transport semiconductor when light-doped. Therefore, the perovskite may be n-type or p-type, or it may be an intrinsic semiconductor. In a preferred embodiment, the perovskite employed is a perovskite that acts as an n-type electron transport semiconductor when light-doped. The perovskite material may exhibit bipolar charge transport and therefore act as both an n-type semiconductor and a p-type semiconductor. Specifically, depending on the type of junction formed between the perovskite and the adjacent material, the perovskite may act as both an n-type semiconductor and a p-type semiconductor.

[0083] Typically, the perovskite semiconductor used in the present invention is a photosensitive material, ie, a material capable of simultaneously performing photogeneration and charge transport.

[0084] As used herein, the term "mixed anion" refers to a compound containing at least two different anions. The term "halide" refers to an anion of an element selected from Group 17 of the periodic table, i.e., a halogen anion. Typically, a halide anion refers to a fluoride anion, a chloride anion, a bromide anion, an iodide anion, or an astatide anion.

[0085] As used herein, the term "metal halide perovskite" refers to a perovskite whose formula comprises at least one metal cation and at least one halide anion. As used herein, the term "organometallic halide perovskite" refers to a metal halide perovskite whose formula comprises at least one organic cation.

[0086] The term "organic material" has its ordinary meaning in the art. Typically, an organic material refers to a material comprising one or more compounds that contain carbon atoms. As will be understood by the skilled artisan, an organic compound may include a carbon atom covalently bonded to another carbon atom, or to a hydrogen atom, or to a halogen atom, or to a chalcogen atom (e.g., an oxygen atom, a sulfur atom, a selenium atom, or a tellurium atom). The skilled artisan will understand that the term "organic compound" does not typically include, for example, compounds that are primarily ionic, such as carbides.

[0087] The term "organic cation" refers to a cation that contains carbon. The cation may contain other elements, for example, the cation may contain hydrogen, nitrogen or oxygen.

[0088] As used herein, the term "semiconductor" refers to a material having an electrical conductivity between that of a conductor and a dielectric. A semiconductor may be an n-type semiconductor, a p-type semiconductor, or an intrinsic semiconductor.

[0089] As used herein, the term "dielectric" refers to a material that is an electrical insulator or a very poor conductor of current. The term dielectric therefore excludes semiconductor materials such as titanium dioxide. As used herein, the term dielectric generally refers to a material having a band gap equal to or greater than 4.0 eV (the band gap of titanium dioxide is approximately 3.2 eV).

[0090] The term "n-type" as used herein refers to a region, layer or material comprising an extrinsic semiconductor having a greater concentration of electrons than holes. In an n-type semiconductor, electrons are therefore majority carriers and holes are minority carriers, and therefore they are electron transport materials. Therefore, the term "n-type region" as used herein refers to a region of one or more electron transport (i.e., n-type) materials. Similarly, the term "n-type layer" refers to a layer of electron transport (i.e., n-type) material. The electron transport (i.e., n-type) material can be a single electron transport compound or elemental material, or a mixture of two or more electron transport compounds or elemental materials. The electron transport compound or elemental material can be undoped or doped with one or more dopant elements.

[0091] The term "p-type" as used herein refers to a region, layer or material comprising an extrinsic semiconductor having a greater concentration of holes than electrons. In a p-type semiconductor, holes are the majority carriers and electrons are the minority carriers, and therefore they are hole transport materials. Therefore, the term "p-type region" as used herein refers to a region of one or more hole transport (i.e., p-type) materials. Similarly, the term "p-type layer" refers to a layer of hole transport (i.e., p-type) material. The hole transport (i.e., p-type) material can be a single hole transport compound or elemental material, or a mixture of two or more hole transport compounds or elemental materials. The hole transport compound or elemental material can be undoped or doped with one or more dopant elements.

[0092] As used herein, the term "band gap" refers to the energy difference between the top of the valence band and the bottom of the conduction band in a material. A skilled artisan can readily measure the band gap of a material without undue experimentation.

[0093] As used herein, the term "layer" refers to any structure that is substantially laminar in form (e.g., extending substantially in two perpendicular directions but limited in extension in a third perpendicular direction). A layer may have a thickness that varies within the layer. Typically, a layer has a substantially constant thickness. As used herein, the "thickness" of a layer refers to the average thickness of the layer. The thickness of a layer can be readily measured, for example, by using microscopy (such as electron microscopy of a cross section of a film) or by surface profile measurement, for example, using a stylus profilometer.

[0094] As used herein, the term "porous" refers to a material having pores arranged therein. Thus, for example, in a porous material, the pores are the volumes within the bulk of the material where no material is present. The individual pores may be of the same size or of different sizes. The size of the pores is defined as the "pore diameter". For most phenomena involving porous solids, the limiting size of a pore is the size of its smallest dimension, which, without any further precision, is referred to as the width of the pore (i.e., the width of a slit-like pore, the diameter of a cylindrical or spherical pore, etc.). When comparing cylindrical pores and slit-like pores, the diameter of the cylindrical pore (rather than its length) should be used as its "pore width" to avoid misleading changes in proportion (Rouquerol, J. et al., (1994) Recommendations for the characterization of porous solids (Technical Report), Pure and Applied Chemistry, 66(8)). The following distinctions and definitions are adopted from the previous IUPAC document (J. Haber., (1991) Manual on catalyst characterization (Recommendations 1991), Pure and Applied Chemistry): micropores have a width (i.e., pore size) of less than 2 nm; mesopores have a width (i.e., pore size) of 2 nm to 50 nm; and macropores have a width (i.e., pore size) of greater than 50 nm. In addition, nanopores can be considered to have a width (i.e., pore size) of less than 1 nm.

[0095] Porosity in a material can include both "closed" pores and open pores. Closed pores are pores in a material that are non-connected cavities—that is, pores that are isolated within the material and not connected to any other pores, and therefore cannot enter the fluids to which the material is exposed. On the other hand, "open pores" can allow such fluids to enter. J. Rouquerol et al. discuss the concepts of open and closed porosity in detail.

[0096] Thus, open porosity refers to the fraction of the total volume of a porous material through which fluid flow can effectively occur. Closed pores are therefore excluded. The term "open porosity" is interchangeable with the terms "connected porosity" and "effective porosity" and is often simply simplified to "porosity" in the art. As used herein, the term "no open porosity" therefore refers to a material that has no effective porosity. Thus, a material without open porosity typically has no macropores and no mesopores. However, a material without open porosity can include micropores and nanopores. Such micropores and nanopores are generally too small to negatively impact materials that require low porosity.

[0097] Furthermore, a polycrystalline material is a solid composed of many individual crystallites or grains, wherein the grain boundaries are located at the interface between any two crystallites or grains in the material. Thus, a polycrystalline material can have intergranular / interstitial porosity and intragranular / internal porosity. The terms "intergranular porosity" and "interstitial porosity" as used herein refer to the pores between the crystallites or grains (i.e., grain boundaries) of a polycrystalline material, while the terms "intragranular porosity" and "internal porosity" as used herein refer to the pores within the individual crystallites or grains of a polycrystalline material. In contrast, a single crystal or single crystalline material is a solid in which the crystal lattice is continuous and uninterrupted throughout the volume of the material, such that there are no grain boundaries and no intergranular / interstitial porosity.

[0098] As used herein, the term "dense layer" refers to a layer that lacks mesoporosity or macroporosity. A dense layer may sometimes have microporosity or nanoporosity.

[0099] Thus, the term "scaffold material" as used herein refers to a material that is capable of acting as a support for another material. Thus, the term "porous scaffold material" as used herein refers to a material that is itself porous and is capable of acting as a support for another material.

[0100] As used herein, the term "transparent" refers to a material or object that allows visible light to pass through with little interference so that objects behind can be clearly seen. Thus, as used herein, the term "translucent" refers to a material or object that has a transmittance (alternatively and equivalently referred to as transmittance) for visible light that is intermediate between that of a transparent material or object and that of an opaque material or object. Typically, a transparent material will have an average transmittance of about 100% or 90% to 100% for visible light (typically light with a wavelength of 370nm to 740nm). Typically, an opaque material will have an average transmittance of about 0% or 0% to 5% for visible light. A translucent material or object will typically have an average transmittance of 10% to 90% for visible light, typically 40% to 60%. Unlike many semi-transparent objects, translucent objects generally do not distort or blur images. Transmission of light can be measured using conventional methods, such as by comparing the intensity of the incident light with the intensity of the transmitted light.

[0101] As used herein, the term "electrode" refers to a conductive material or object through which an electric current enters or leaves an object, substance, or region. As used herein, the term "negative electrode" refers to an electrode through which electrons leave a material or object (i.e., an electron collecting electrode). The negative electrode is commonly referred to as the "anode." As used herein, the term "positive electrode" refers to an electrode through which holes leave a material or object (i.e., a hole collecting electrode). The positive electrode is commonly referred to as the "cathode." In a photovoltaic device, electrons flow from the positive electrode / cathode to the negative electrode / anode, while holes flow from the negative electrode / anode to the positive electrode / cathode.

[0102] As used herein, the term "front electrode" refers to an electrode disposed on the side or surface of a photovoltaic device that is intended to be exposed to sunlight. Therefore, the front electrode typically needs to be transparent or translucent to allow light to pass through the electrode to the photosensitive layer disposed below the front electrode. Therefore, as used herein, the term "back electrode" refers to an electrode disposed on the side or surface of a photovoltaic device that is opposite to the side or surface that is intended to be exposed to sunlight.

[0103] The term "charge transporter" refers to an area, layer, or material through which charge carriers (i.e., particles that carry an electric charge) can move freely. In semiconductors, electrons act as mobile negative charge carriers, and holes act as mobile positive charges. Therefore, the term "electron transporter" refers to an area, layer, or material through which electrons can easily flow and will generally reflect holes (a hole is a lack of electrons that are considered mobile carriers of positive charge in a semiconductor). Conversely, the term "hole transporter" refers to an area, layer, or material through which holes can easily flow and will generally reflect electrons.

[0104] The term "consisting essentially of" means that a composition comprises the components that it essentially comprises, as well as other components, provided that the other components do not materially affect the basic characteristics of the composition. Typically, a composition consisting essentially of certain components will contain greater than or equal to 95% by weight of those components or greater than or equal to 99% by weight of those components.

[0105] As used herein, the term "volatile compound" refers to a compound that is easily removed by evaporation or decomposition. For example, a compound that is easily removed by evaporation or decomposition at a temperature of less than or equal to 150°C, or for example at a temperature of less than or equal to 100°C, is a volatile compound. "Volatile compound" also includes compounds that are easily removed by evaporation of decomposition products. Thus, a volatile compound X can be easily evaporated by evaporation of molecules of X, or a volatile compound X can be easily evaporated by decomposing to form two compounds Y and Z that are easily evaporated. For example, an ammonium salt can be a volatile compound and can evaporate into molecules of the ammonium salt or into decomposition products, such as ammonium and a hydrogen compound (e.g., a hydrogen halide). Thus, a volatile compound X can have a relatively high vapor pressure (e.g., greater than or equal to 500 Pa) or can have a relatively high decomposition pressure (e.g., greater than or equal to 500 Pa for one or more of the decomposition products), which can also be referred to as a dissociation pressure.

[0106] As used herein, the term "roughness" refers to the texture of a surface or edge that is not flat or irregular (and therefore lacks smoothness or regularity). The roughness of a surface can be quantified by any measure of the surface's deviation in a direction generally perpendicular to the average surface. As a measure of roughness, the roughness average or mean roughness (R a) is the arithmetic mean of the absolute values of all deviations from a straight line within a specified reference or sampling length of the surface profile. As an alternative measure of roughness, the root mean square roughness (R rms or R q ) is the root mean square of the values of all deviations from a straight line within a specified reference or sampling length of the surface profile.

[0107] Device structure

[0108] Figure 1 A single-junction photovoltaic device 100 is schematically shown comprising a transparent or semi-transparent front electrode 101 and a back electrode 102, wherein a photoactive region 110 is disposed between the front and back electrodes, wherein the photoactive region comprises a perovskite material of general formula (I):

[0109] [A][B][X]3(I)

[0110] wherein [A] is at least one monovalent cation, [B] is at least one divalent inorganic cation, and [X] is at least one halide anion.

[0111] The perovskite material is configured to act as a light absorber / photosensitizer in the photosensitive region. In addition, the perovskite material in the photosensitive region can also be configured to provide charge transport. In this regard, the perovskite material can not only act as a light absorber (i.e., a photosensitizer), but also as an n-type, p-type, or intrinsic (i-type) semiconductor material (charge transporter). The perovskite material can therefore act as both a photosensitizer and an n-type semiconductor material. The perovskite material can therefore take on the roles of both light absorption and long-range charge transport.

[0112] Figure 2a and Figure 2b A separate structure for a single-junction photovoltaic device 100 is schematically shown, wherein a photoactive region 110 comprises a perovskite material of formula (I). In each of these embodiments, the photoactive region 110 comprises an n-type region 111 having at least one n-type layer, a p-type region 112 having at least one p-type layer, and a layer of perovskite material 113 disposed between the n-type and p-type regions.

[0113] Figure 2aThe device shown has a structure that is considered to be a regular structure for a perovskite-based single-junction photovoltaic device, in which the front electrode 101 is in contact with the n-type region 111 of the photoactive region 110 and the back electrode 102 is in contact with the p-type region 112 of the photoactive region 110 (see, for example, Docampo, P et al., (2013) Efficient organometal trihalideperovskite planar-heterojunction solar cells on flexible polymer substrates, Nat Comms, 4). Therefore, the front electrode 101 acts as a negative (electron collecting) electrode, while the back electrode 102 acts as a positive (hole collecting) electrode.

[0114] As an example, in Figure 2a In the exemplary device structure shown, the front electrode may include a transparent conductive oxide (TCO) such as tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), etc., the n-type region may include one or more n-type material layers (e.g., wherein each layer of n-type material may include an n-type material selected from those detailed above), the p-type region may include one or more p-type material layers (e.g., wherein each layer of p-type material may include a p-type material selected from those detailed above), and the back electrode may include a high work function metal such as gold (Au), silver (Ag), nickel (Ni), palladium (Pd), platinum (Pt), or aluminum (Al).

[0115] on the contrary, Figure 2b The device shown has a structure that is considered to be an inverted structure for perovskite-based single-junction photovoltaic devices, where the front electrode 101 is in contact with the p-type region 112 of the photoactive region 110 and the back electrode 102 is in contact with the n-type region 111 of the photoactive region 110. Therefore, the front electrode 101 acts as a positive (hole-collecting) electrode, while the back electrode 102 acts as a negative (electron-collecting) electrode.

[0116] As an example, in Figure 2b In the exemplary device structure shown, the front electrode may include a transparent conductive oxide (TCO) such as tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), etc., the p-type region may include one or more p-type material layers (e.g., wherein each layer of p-type material may include a p-type material selected from those detailed above), the n-type region may include one or more n-type material layers (e.g., wherein each layer of n-type material may include an n-type material selected from those detailed above), and the back electrode may include a high work function metal such as gold (Au), silver (Ag), nickel (Ni), palladium (Pd), platinum (Pt) or aluminum (Al).

[0117] Figure 2a and2b Both devices shown in the embodiment include an n-type region and a p-type region, wherein the photosensitive perovskite material is arranged between the n-type region and the p-type region, so that the n-type (electron transport) region and the p-type (hole transport) region act to transport the charge generated in the perovskite material toward the respective electrodes. However, such devices can also include only one charge transport region. In particular, it has been shown that functional photovoltaic devices containing photosensitive perovskites can be formed without any hole transport material, so that the photosensitive perovskite is in direct contact with the electrodes and / or metal layers (see Etgar, L, Gao, P. & Xue, Z., 2012, Mesoscopic CH3NH3Pbl3 / TiO2 heterojunction solar cells, J.Am.Chem.Soc, 2012, 134(42), pp. 17396-17399). In such devices, the photosensitive perovskite acts as both a light collector and a hole transporter, making additional hole transport material redundant.

[0118] Figures 3a to 3c Some detailed examples of perovskite-based single-junction photovoltaic devices are shown.

[0119] exist Figure 3a and Figure 3b In the embodiment of the present invention, the photoactive region 110 of the photovoltaic device 100 includes a porous region 114, wherein the porous region 114 includes a layer of a perovskite material 113 of formula (I) in contact with a porous scaffold material 115 disposed between an n-type region 111 and a p-type region 112. In these structures, the layer of perovskite material 113 is provided as a coating on the porous scaffold material 115, thereby forming a substantially conformal layer on the surface of the porous scaffold, such that the perovskite material 113 is disposed within the pores of the porous scaffold. The p-type region 112 contains a charge transport material, which then fills the pores of the porous region 114 (i.e., the pores of the perovskite-coated porous scaffold) and forms a capping layer on the porous material. In this regard, the capping layer of charge transport material consists of a layer of charge transport material without open porosity.

[0120] exist Figure 3a In the figure, the photovoltaic device 100 is shown having an architecture that has been referred to as an extremely thin absorber (ETA) cell architecture, in which an extremely thin layer of light-absorbing perovskite material is provided at the interface between nanostructured, interpenetrating n-type (e.g., TiO2) and p-type semiconductors (e.g., HTM). In this arrangement, the porous scaffold material 115 within the photoactive region 110 contains the semiconductor / charge transport material.

[0121] exist Figure 3bIn the illustrated photovoltaic device 100, an architecture known as a meso-superstructure solar cell (MSSC) architecture is employed, in which a very thin layer of a light-absorbing perovskite material is disposed on a mesoporous insulating support material. In this arrangement, the porous support material 115 within the photoactive region 110 comprises a dielectric material (e.g., Al2O3).

[0122] exist Figure 3c In the embodiment of the present invention, the photosensitive region 110 includes a layer of a perovskite material 113 of formula (I) without open porosity. As described above, materials without open porosity generally have no macropores and no mesopores, but may have micropores and nanopores (and therefore may have intercrystalline pores). The layer of perovskite material 113 thus forms a planar heterojunction with one or both of the n-type region 111 and the p-type region 112. The n-type region 111 or the p-type region 112 may be disposed on the layer of perovskite material 113 without open porosity. In this regard, because the layer of perovskite material 113 has no open porosity, no n-type or p-type material penetrates the perovskite material to form a bulk heterojunction; instead, it forms a planar heterojunction with the perovskite material. Typically, the layer of perovskite material 113 without open porosity is in contact with both the n-type region and the p-type region, and thus forms a planar heterojunction with both the n-type region and the p-type region.

[0123] exist Figure 3c The photovoltaic device 100 shown in FIG. 1 thus has a thin-film planar heterojunction device architecture in which a thin solid layer of light-absorbing perovskite material is disposed between planar layers of n-type (e.g., TiO2) and p-type semiconductors (e.g., HTM). In this arrangement, the device does not include a porous scaffold material.

[0124] In an alternative configuration, the photosensitive region can include a layer of a perovskite material having formula (I), wherein the perovskite material fills the pores of a porous scaffold material and forms a capping layer of the perovskite material on the porous scaffold material, wherein the porous scaffold material does not penetrate the capping layer of the perovskite material. The layer of the perovskite material is thus in contact with the porous scaffold material. Typically, the capping layer consists of a layer of the perovskite material that has no open porosity and thus forms a planar heterojunction with one of the n-type region and the p-type region.

[0125] In another configuration, the photosensitive region can include a layer of a perovskite material of formula (I), wherein the perovskite material itself is porous. A charge transport material then fills the pores of the porous region of the perovskite material and forms a capping layer on the porous perovskite material. In this regard, the capping layer of charge transport material consists of a layer of charge transport material without open porosity.

[0126] Figure 4A multi-junction photovoltaic device 200 is then shown, comprising a first subcell 210 in which the photoactive region 110 comprises a perovskite material having the general formula (I) and one or more further subcells 220 disposed between a front electrode 201 and a back electrode 202. Specifically, Figure 4 A monolithically integrated multi-junction photovoltaic device is shown, in which each sub-cell 110b, 120 is connected to an adjacent sub-cell via an intermediate region 230 comprising one or more interconnecting layers (e.g., a recombination layer or tunnel junction). In a monolithically integrated multi-junction photovoltaic device, the sub-cells are electrically connected in series, which results in the need for a recombination layer or tunnel junction and current matching. In contrast, in a mechanically stacked multi-junction photovoltaic device, the sub-cells are provided with separate electrical contacts and, therefore, do not require current matching. However, the additional size and cost of the additional contacts and substrate, as well as the difficulty in heat dissipation, make the mechanical stacking structure less advantageous than the monolithic integrated structure.

[0127] Figure 5a and Figure 5b A single embodiment of a multijunction photovoltaic device 200 is schematically shown having a first subcell 210 in which the photoactive region 110 comprises a perovskite material of formula (I) and one or more further subcells 220 .

[0128] In each of these embodiments, the multi-junction photovoltaic device 200 has a monolithic integrated structure that includes only two electrodes, a front electrode 201 and a back electrode 202, with a first subcell 210 and one or more other subcells 220 disposed therebetween. Furthermore, because the monolithic integrated structure includes only two electrodes, each subcell is connected to an adjacent subcell via an intermediate region 230, each of which includes one or more interconnect layers. For example, the interconnect layer may include a composite layer or a tunnel junction.

[0129] In each of these embodiments, the photosensitive region 110 of the first subcell 210 can have the same structure as any of the photosensitive regions described above. Figure 5a and Figure 5b In the embodiment shown, the photosensitive region 110 may have Figure 3a Alternatively, the photoactive region 110 of the first subcell 210 may have the same structure as the photoactive region of the extremely thin absorber (ETA) cell architecture of the single junction device shown. Figure 3b As another alternative, the photosensitive region 110 of the first subcell 210 may have the same structure as the photosensitive region of the medium-scale superstructure solar cell (MSSC) architecture of the single junction device shown in FIG. Figure 3c The photoactive region of the thin-film planar heterojunction device architecture shown is identical to the structure of the single-junction device.

[0130] In each of these embodiments, as in a single-junction device, the photoactive region 110 of the first subcell 210 includes an n-type region 111 having at least one n-type layer, a p-type region 112 having at least one p-type layer, wherein a layer of perovskite material 113 is disposed between the n-type region 111 and the p-type region 112.

[0131] As an example, each of the one or more other sub-cells 220 of the multi-junction photovoltaic device 200 may include any of a second photosensitive perovskite material, amorphous silicon, crystalline silicon (i.e., single crystal or polycrystalline), CdTe, CuZnSnSSe, CuZnSnS, or CuInGaSe (CIGS).

[0132] Figure 5a The device shown has a structure that is considered to be a regular structure for a perovskite-based multi-junction photovoltaic device 200, where the front electrode 201 is in contact with the p-type region 112 of the photoactive region 110 of the first sub-cell 210, and the back electrode 202 is in contact with one of the one or more other sub-cells 220. Thus, the front electrode 201 acts as a positive (hole-collecting) electrode, while the back electrode 202 acts as a negative (electron-collecting) electrode.

[0133] exist Figure 5a In the figure, the multi-junction photovoltaic device 200 is a series device comprising two sub-cells 210, 220, wherein the top / upper / first sub-cell 210 comprises a photosensitive region 110 comprising a photosensitive / light-absorbing perovskite material 113 of formula (I), and the bottom / lower / second sub-cell 220 can, for example, comprise a crystalline silicon-based sub-cell.

[0134] As an example, in this exemplary structure, the front electrode 201 may include a transparent conductive oxide (TCO), such as tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), etc. The p-type region 112 of the first subcell 210 may include one or more p-type material layers (e.g., each p-type material layer may include a p-type material selected from those detailed above), the n-type region 111 of the first subcell 210 may include one or more n-type material layers (e.g., each n-type material layer may include an n-type material selected from those detailed above), and the back electrode 202 may include a high work function metal, such as gold (Au), silver (Ag), nickel (Ni), palladium (Pd), platinum (Pt), or aluminum (Al). As an example, the intermediate region 230 may include a composite layer having a layer of ITO.

[0135] on the contrary, Figure 5bThe device shown in FIG has a structure that is believed to be an inverted structure for a perovskite-based multi-junction photovoltaic device 200, where a front electrode 201 is in contact with the n-type region 111 of a first sub-cell 210, and a back electrode 202 is in contact with one of the one or more other sub-cells 220. Thus, the front electrode 201 acts as a negative (electron collecting) electrode, while the back electrode 202 acts as a positive (hole collecting) electrode.

[0136] exist Figure 5b , the multi-junction photovoltaic device 200 shown is a tandem device comprising two sub-cells 210, 220, wherein the top / upper / first sub-cell 210 comprises a photosensitive region 110 comprising a photosensitive / light-absorbing perovskite material 113 of formula (I), and the bottom / lower / second sub-cell 220 may, for example, comprise a crystalline silicon-based sub-cell.

[0137] As an example, in this exemplary structure, the front electrode 201 may include a transparent conductive oxide (TCO), such as tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), etc., the n-type region 111 of the first subcell 210 may include one or more n-type material layers (e.g., each n-type material layer may include an n-type material selected from those detailed above), the p-type region 112 of the first subcell 210 may include one or more p-type material layers (e.g., each p-type material layer may include a p-type material selected from those detailed above), and the back electrode 202 may include a high work function metal, such as gold (Au), silver (Ag), nickel (Ni), palladium (Pd), platinum (Pt), or aluminum (Al). As an example, the intermediate region 230 may include a composite layer having a layer of ITO.

[0138] Figures 6a to 6c Some other exemplary embodiments of a multi-junction photovoltaic device having a first subcell and one or more other subcells comprising a photosensitive perovskite material having the general formula (I) are shown. Specifically, Figure 6a An example of a tandem photovoltaic device is shown in which the top / upper / first subcell contains a photosensitive / light-absorbing perovskite material and the bottom / lower / second subcell includes a crystalline silicon subcell. In this exemplary embodiment, the crystalline silicon subcell includes an amorphous silicon / crystalline silicon heterojunction (SHJ) that utilizes a crystalline silicon (c-Si) wafer as the photosensitive absorber and an amorphous silicon (a-Si) thin film for junction formation and surface passivation. The crystalline silicon subcell includes a p-type a-Si emitter, an intrinsic a-Si passivation / buffer layer, an n-type c-Si photosensitive absorber, another intrinsic a-Si passivation / buffer layer, and a back surface field (BSF) layer made of n-type a-Si.

[0139] Figure 6bAn example of a tandem photovoltaic device is shown in which the top / upper / first subcell comprises a photoactive / light-absorbing perovskite material and the bottom / lower / second subcell comprises a CIGS, CIS, or CZTSSe subcell. In this exemplary embodiment, the bottom subcell comprises a (p-type) CIGS, CIS, or CZTSSe photoactive absorber and an (n-type) CdS buffer layer.

[0140] Figure 6c An example of a tandem photovoltaic device is shown where the top / upper / first subcell comprises a photoactive / light-absorbing perovskite material and the bottom / lower / second subcell comprises a second photoactive / light-absorbing perovskite material.

[0141] In the photovoltaic device described above, the n-type region includes one or more n-type layers. Typically, the n-type region is an n-type layer, i.e., a single n-type layer. However, in other embodiments, the n-type region may include an n-type layer and a separate n-type exciton blocking layer or hole blocking layer.

[0142] An exciton blocking layer is a material with a band gap wider than that of the photosensitive material, but whose conduction band or valence band closely matches that of the photosensitive material. If the conduction band (or lowest unoccupied molecular orbital energy level) of the exciton blocking layer is closely aligned with the conduction band of the photosensitive material, electrons can enter and pass through the exciton blocking layer from the photosensitive material, or pass through the exciton blocking layer and enter the photosensitive material, and this is called an n-type exciton blocking layer. An example of this is bathocuproine (BCP), as described in P. Peumans, A. Yakimov, and S.R. Forrest, "Small molecular weight organic thin-film photodetectors and solar cells", J. Appl. Phys., Phys. Masaya Hirade and Chihaya Adachi, "Small molecular organic photovoltaic cells with exciton blocking layer at anode interface for improved device performance", Appl. Phys. Lett. 99, 153302 (2011).

[0143] The n-type layer is a layer of electron-transporting (i.e., n-type) material. The n-type material can be a single n-type compound or elemental material, or a mixture of two or more n-type compounds or elemental materials, which can be undoped or doped with one or more dopant elements. The n-type layer can comprise inorganic or organic n-type materials.

[0144] Suitable inorganic n-type materials can be selected from metal oxides, metal sulfides, metal selenides, metal tellurides, perovskites, amorphous silicon, n-type Group IV semiconductors, n-type Group III-V semiconductors, n-type Group II-VI semiconductors, n-type Group I-VII semiconductors, n-type Group IV-VI semiconductors, n-type Group V-VI semiconductors, and n-type Group II-V semiconductors, any of which may be doped or undoped. Typically, the n-type material is selected from metal oxides, metal sulfides, metal selenides, and metal tellurides. Thus, the n-type material may comprise an inorganic material selected from the group consisting of oxides of titanium, tin, zinc, niobium, tantalum, tungsten, indium, gallium, neodymium, palladium, cadmium, or oxides of mixtures of two or more of the metals; sulfides of cadmium, tin, copper, zinc, or sulfides of mixtures of two or more of the metals; selenides of cadmium, zinc, indium, gallium, or selenides of mixtures of two or more of the metals; or tellurides of cadmium, zinc, cadmium, or tin, or tellurides of mixtures of two or more of the metals.

[0145] Examples of other semiconductors that may be suitable n-type materials (e.g., if they are n-doped) include Group IV element or compound semiconductors; amorphous silicon; Group III-V semiconductors (e.g., gallium arsenide); Group II-VI semiconductors (e.g., cadmium selenide); Group I-VII semiconductors (e.g., cuprous chloride); Group IV-VI semiconductors (e.g., lead selenide); Group V-VI semiconductors (e.g., bismuth telluride); and Group II-V semiconductors (e.g., cadmium arsenide).

[0146] Other n-type materials, including organic and polymeric electron transport materials and electrolytes, may also be employed. Suitable examples include, but are not limited to, fullerenes or fullerene derivatives, organic electron transport materials comprising perylene or its derivatives, or poly{[N,NO-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(imide)-2,6-diyl]-salt-5,50-(2,20-thiophene)} (P(NDI20D-T2)).

[0147] In the above-mentioned photovoltaic device, the p-type region includes one or more p-type layers. Typically, the p-type region is a p-type layer, i.e., a single p-type layer. However, in other embodiments, the p-type region may include a p-type layer and a p-type exciton blocking layer or an electron blocking layer. If the valence band (or highest occupied molecular orbital energy level) of the exciton blocking layer is closely aligned with the valence band of the photosensitive material, holes can enter from the photosensitive material and pass through the exciton blocking layer, or pass through the exciton blocking layer and enter the photosensitive material, and we call this a p-type exciton blocking layer. An example of this is tris[4-(5-phenylthiophen-2-yl)phenyl]amine, as described by Masaya Hirade and Chihaya Adachi, “Small molecular organic photovoltaic cells with excitonblocking layer at anode interface for improved device performance”, Appl. Phys. Lett. 99, 153302 (2011).

[0148] The p-type layer is a layer of hole-transporting (i.e., p-type) material. The p-type material can be a single p-type compound or elemental material, or a mixture of two or more p-type compounds or elemental materials, which can be undoped or doped with one or more dopant elements. The p-type layer can comprise inorganic or organic p-type materials.

[0149] Suitable p-type materials can be selected from polymers or molecular hole transporters. Suitable p-type materials include molecular hole transporters, polymer hole transporters and copolymer hole transporters. The p-type material can be, for example, a hole transport material, polymer or copolymer comprising one or more of the following groups: phenylthio, phenalene, dithiazolyl, benzothiazolyl, diketopyrrolopyrrole, ethoxydithiazyl, amino, triphenylamino, carbazolyl, ethylenedioxyphenylthio, dioxyphenylthio, or fluorenyl. Therefore, the p-type material used in the optoelectronic device of the present invention can include, for example, any of the aforementioned molecular hole transport materials, polymers or copolymers. In one embodiment, the p-type region comprises a hole transport material.

[0150] The p-type layer of the photovoltaic device may include spiro-OMeTAD (2,2',7,7'-tetrakis-(N,N-di-p-methoxyaniline)-9,9'-spirobifluorene)), P3HT (poly(3-hexylthiophene)), PCPDTBT (poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl]]), PVK (poly(N-vinylcarbazole)), poly(3-hexylthiophene) ), poly[N,N-diphenyl-4-methoxyaniline-4',4"-diyl], sexithiophene, 9,10-bis(phenylethynyl)anthracene, 5,12-bis(phenylethynyl)tetracene, diindeno, 9,10-diphenylanthracene, PEDOT-TMA, PEDOT:PSS, perfluoropentacene, perylene, poly(p-phenylene oxide), poly(p-phenylene sulfide), quinacridone, rubrene, 4-(dimethylamino)benzaldehyde diphenylhydrazone, 4-(dibenzylamino)benzaldehyde-N,N-diphenylhydrazone or phthalocyanine.

[0151] Depending on the specific arrangement of any of the above-mentioned photosensitive devices, the thickness of the photosensitive region is typically 300 nm to 3000 nm. Typically, the thickness of the photosensitive region is 400 nm to 2000 nm. For example, the thickness may be 500 nm to 1500 nm.

[0152] The perovskite material layer preferably comprises a thin film of the perovskite material. In this regard, in order to provide a high-efficiency photovoltaic device, the absorption of the absorber should ideally be maximized in order to produce an optimal amount of current. Therefore, when using perovskites as absorbers in photovoltaic devices, the thickness of the perovskite layer should ideally be approximately 300nm to 600nm in order to absorb sunlight across most of the visible spectrum. Specifically, in solar cells, the perovskite layer should generally be thicker than the absorption depth (which is defined as the thickness of the film required to absorb 90% of the incident light of a given wavelength, which for the perovskite material in question is typically 100nm or more if significant light absorption is required across the entire visible spectrum (400nm to 800nm)), because using a photosensitive layer with a thickness of less than 100nm in a photovoltaic device may adversely affect the performance of the device.

[0153] Thus, typically, the thickness of the layer of perovskite material is between 50 nm and 2 μm. The thickness of the layer of perovskite material in the photovoltaic device may be, for example, 100 nm to 1000 nm. The thickness of the layer of perovskite material in the photovoltaic device may be, for example, 200 nm to 700 nm, and preferably 300 nm to 600 nm.

[0154] In the photovoltaic device described above, the front electrode may have a thickness of 100 nm to 700 nm, for example, 100 nm to 400 nm. For example, the thickness may be 400 nm. The back electrode may have a thickness of 10 nm to 500 nm, for example, 50 nm to 200 nm. For example, the back electrode may have a thickness of 150 nm.

[0155] The n-type region may have a thickness of 50 nm to 1000 nm. For example, the n-type region may have a thickness of 50 nm to 500 nm or 100 nm to 500 nm. In the case where the n-type region comprises a dense layer of n-type semiconductor, the dense layer has a thickness of 50 nm to 200 nm, typically about 100 nm.

[0156] The p-type region may have a thickness of 50 nm to 1000 nm. For example, the p-type region may have a thickness of 50 nm to 500 nm or 100 nm to 500 nm.

[0157] In the case where the photosensitive region comprises a porous scaffold, the thickness of the porous scaffold layer may be 5 nm to 500 nm or 100 nm to 300 nm. For example, the thickness of the porous scaffold layer may be 10 nm to 50 nm.

[0158] In the case where the photosensitive region includes a capping layer of perovskite material over the porous region, the thickness of the capping layer can be greater than, equal to, or less than the thickness of the porous region. The capping layer typically has a thickness of 10 nm to 1000 nm, or, for example, 100 nm to 700 nm. It is generally preferred that the capping layer have a thickness of at least 100 nm. The thickness of the porous region typically has a thickness of 5 nm to 1000 nm. More typically, the thickness of the porous region has a thickness of 5 nm to 500 nm, or, for example, 30 nm to 200 nm.

[0159] Figure 7a and Figure 7b Schematically depicted is a close-up view of an exemplary embodiment of a multi-junction photovoltaic device in which a conformal layer of a photoactive perovskite material has been deposited onto a rough or textured surface according to the methods described herein.

[0160] Figure 7a Schematically depicted is a textured / roughened top surface 221 of an additional subcell 220 located directly beneath a first subcell 210 comprising a perovskite material 113 having the general formula (I). Depending on whether the device has a regular or inverted structure, a conformal n-type region 111 or p-type region 112 is deposited onto the textured / roughened top surface 221 of the additional photoactive region 220. A layer of perovskite material 113 is subsequently deposited onto the roughened / textured surface presented by the conformal n-type region 111 or p-type region 112 present on the textured / roughened top surface of the additional subcell 220.

[0161] Figure 7b The textured / roughened top surface 221 of the other subcell 220 is schematically shown, located directly below the first subcell 210 comprising the perovskite material 113 of the general formula (I). In this device, the other subcell 220 is separated from the first subcell 210 by a conformal intermediate region 230 deposited onto the textured / roughened top surface 221 of the other subcell 220. Depending on whether the device has a regular or inverted structure, a conformal n-type region 111 or p-type region 112 is subsequently deposited onto the top surface of the conformal intermediate region 230 (which is itself rough due to conforming to the textured / roughened top surface 221 of the other subcell 220). A layer of perovskite material 113 is then deposited onto the roughened / textured surface presented by the conformal n-type region 111 or p-type region 112 present on the top surface of the conformal intermediate region 230.

[0162] In a multi-junction photovoltaic device, the thickness of the intermediate region 230 connecting the first subcell 210 to the adjacent second subcell is typically 50 nm or less. Therefore, the layer or layers comprising the intermediate region 230 must generally conform to the surface of the second subcell on which they are disposed, with only a negligible smoothing effect on the surface profile of the second subcell.

[0163] The surface roughness / profile of the other subcells 220 located directly below the first subcell 210 may be provided by the surface roughness and / or texture of one of the photoactive layers of the other subcells 220. As an example, Figure 6a In the amorphous silicon / crystalline silicon heterojunction (SHJ) shown, the crystalline silicon layer may be provided with a root mean square roughness (R rms ) will have a textured top surface (e.g., to reduce reflections). The amorphous silicon layers (i and p) above the crystalline silicon layer will then be thin relative to the crystalline silicon layer and will therefore need to conform to the texture of the top surface. As another example, in Figure 6bIn the tandem device shown, the CIGS, CIS, or CZTSSe photoactive absorber layer can be formed with surface roughness (e.g., to scatter light into the absorber layer). The CdS buffer layer above the CZTSSe photoactive absorber layer will then be thin relative to the CZTSSe layer and will therefore need to conform to the rough top surface. Alternatively, a buffer layer or window layer can be disposed within the other subcell 220 located directly below the first subcell 210, and the buffer layer or window layer can be formed with surface roughness such that the top surface of the other subcell 220 presents a rough surface to the first subcell 210. Reference: Hupkes, J., Pust, S. & Bottler, W., 2009. Light scattering and trapping in different thin film photovoltaic devices, Proceeding of the 24th EU Photovoltaic Solar Energy Conference, pp. 2766-2769 (September) Pages 2766-2769 disclose some exemplary values of surface roughness of some conventional photoactive layers (e.g., polysilicon, CIGS, etc.) and some conventional surface textured films used for light trapping in photovoltaic devices, where the measured RMS roughness (R q ) between 65nm and 240nm.

[0164] Method for manufacturing a photovoltaic device

[0165] A method of manufacturing a photovoltaic device is also provided, the photovoltaic device comprising a photosensitive region comprising a perovskite material, wherein the perovskite material layer is provided on a substrate having a roughness average value (R a ) or root mean square roughness (R rms) on the surface of the perovskite material. In this regard, the method includes using vapor deposition to deposit a substantially continuous and conformal solid layer of one or more initial / initial precursor compounds comprising the perovskite material onto the rough surface, and subsequently treating the solid layer of the one or more initial precursor compounds with one or more other / secondary precursor compounds. Treating the solid layer comprising the one or more initial precursor compounds with one or more other precursor compounds causes the one or more initial precursor compounds and the one or more other precursor compounds to react and form a substantially continuous and conformal solid layer of the perovskite material on the rough surface. The step of treating the solid layer comprising the one or more initial precursor compounds preferably includes using solution deposition to treat the solid layer comprising the one or more initial precursor compounds with a solution comprising the one or more other precursor compounds. Alternatively, the step of treating the solid layer comprising the one or more initial precursor compounds includes using vapor deposition to treat the solid layer comprising the one or more initial precursor compounds with one or more other precursor compounds.

[0166] As mentioned above, the perovskite material layer preferably comprises a thin film of the perovskite material. Thus, the thickness of the thin film of the perovskite material is typically 50 nm to 2 μm, usually 100 nm to 1000 nm, and preferably 200 nm to 700 nm.

[0167] The roughness of the surface onto which the perovskite material is deposited will depend on the specific structure of the photovoltaic device. Specifically, for a multi-junction device, the roughness of the surface is defined / determined by the roughness and / or texture present on the top surface of the subcell directly below the perovskite material within the device, e.g. Figure 7a and Figure 7b As shown. By way of example only, the height of the pyramidal features present on a textured solar cell (such as a textured silicon cell) is typically in the range of 50 nm to 30 μm, more typically between 500 nm and 20 μm, and often in the range of 1 μm to 10 μm. Thus, the surface onto which the perovskite material is deposited may have a roughness average value (R) of 50 nm to 30 μm, more typically 500 nm to 20 μm, and often 1 μm to 10 μm. a ) or root mean square roughness (R rms ).

[0168] As detailed above, the perovskite material preferably comprises a perovskite of formula (I)

[0169] [A][B][X]3 (I)

[0170] wherein [A] is at least one monovalent cation, [B] is at least one divalent inorganic cation, and [X] is at least one halide anion.

[0171] [X] preferably comprises at least one halide anion selected from fluoride, chloride, bromide and iodide, and preferably selected from bromide and iodide. Specifically, [X] typically comprises two different halide anions selected from fluoride, chloride, bromide and iodide, and preferably comprises bromide and iodide. For example, [X] may comprise iodide and bromide, with the ratio of iodide to bromide being 3-y:y, where 0 <y<3。

[0172] [A] preferably comprises a compound selected from methylammonium (CH3NH3 + ), formamidine (HC(NH)2)2 + ) and ethylammonium (CH3CH2NH3 + ) at least one organic cation. Alternatively or in addition, [A] may comprise an organic cation selected from Cs + , Rb + 、Cu + 、Pd + , Pt + 、Ag + 、Au + , Rh + and Ru + , and is preferably selected from Cs + and Rb + at least one inorganic cation, and more preferably Cs + Thus [A] may comprise organic cations (A) and inorganic cations (A'), the ratio of organic cations (A) to inorganic cations (A') being 1-x:x, wherein 0 <x<1。

[0173] [B] preferably contains a compound selected from Pb 2+ and Sn 2+ at least one divalent inorganic cation, and more preferably comprises a lead (II) cation (Pb 2+ ).

[0174] In one embodiment, each of the one or more initial precursor compounds comprises one of the one or more divalent inorganic cations [B], and each of the one or more additional precursor compounds comprises one of the one or more monovalent cations [A]. By way of example, when [B] comprises a first divalent inorganic cation B and a second divalent inorganic cation B', the one or more initial precursor compounds typically include at least a first initial precursor compound comprising the first divalent inorganic cation B and a second initial precursor compound comprising the second divalent inorganic cation B'. By way of example, when [B] comprises / consists of a divalent inorganic cation B, the one or more initial precursor compounds typically include at least at least one initial precursor compound comprising the divalent inorganic cation B. By way of further example, when [A] comprises a first monovalent cation A and a second monovalent cation A', the one or more additional precursor compounds typically include at least a first additional precursor compound comprising the first monovalent cation A and a second additional precursor compound comprising the second monovalent cation A'. In yet another example, when [A] comprises / consists of a monovalent cation A, the one or more additional precursor compounds typically include at least at least one additional precursor compound comprising a first monovalent cation A.

[0175] Each of the one or more first precursor compounds and each of the one or more second precursor compounds may further comprise one of the one or more halide anions [X]. As an example, when [X] comprises a first halide anion X and a second halide anion X', at least one of the one or more initial precursor compounds comprises one of the first halide anion X and the second halide anion X', and at least one of the one or more additional precursor compounds comprises the other of the first halide anion X and the second halide anion X'.

[0176] In a more detailed example, when [B] comprises / consists of a divalent inorganic cation B and [X] comprises a first halide anion X and a second halide anion X, then the one or more initial precursor compounds may comprise one or both of the following:

[0177] i) an initial precursor compound comprising a divalent inorganic cation B and a first halide anion X (ie, BX2); and

[0178] ii) an initial precursor compound comprising a divalent inorganic cation B and a second halide anion X' (ie, BX'2).

[0179] Similarly, when [A] comprises a first monovalent cation A and a second monovalent cation A' and [X] comprises a first halide anion X and a second halide anion X', then the one or more other precursor compounds may comprise one or more of the following:

[0180] i) another precursor compound comprising a first monovalent cation A and a first halide anion X (ie, AX);

[0181] ii) another precursor compound comprising a first monovalent cation A and a second halide anion X' (ie, AX');

[0182] iii) another precursor compound comprising a second monovalent cation A' and a first halide anion X (ie, A'X); and

[0183] iv) another precursor compound comprising a second monovalent cation A' and a second halide anion X' (ie, A'X').

[0184] In another embodiment, when [A] comprises one or more inorganic cations, each of the one or more initial precursor compounds may comprise one of the one or more monovalent inorganic cations [A], and each of the one or more additional precursor compounds comprises one of the one or more divalent inorganic cations [B]. By way of example, in this embodiment, when [A] comprises a first monovalent inorganic cation A and a second monovalent inorganic cation A', the one or more initial precursor compounds typically include at least a first initial precursor compound comprising the first monovalent inorganic cation A and a second initial precursor compound comprising the second monovalent inorganic cation A'. By way of example, when [A] comprises / consists of a monovalent inorganic cation A, the one or more initial precursor compounds typically include at least at least one initial precursor compound comprising a monovalent inorganic cation A. As another example of this embodiment, when [B] comprises a first divalent inorganic cation B and a second divalent inorganic cation B', the one or more additional precursor compounds typically include at least a first additional precursor compound comprising the first divalent inorganic cation B and a second additional precursor compound comprising the second divalent inorganic cation B'. As yet another example of this embodiment, when [B] comprises / consists of a divalent inorganic cation B, the one or more additional precursor compounds include at least an initial precursor compound comprising a divalent inorganic cation B.

[0185] Each of the one or more first precursor compounds and each of the one or more second precursor compounds may further comprise one of the one or more halide anions [X]. As an example, when [X] comprises a first halide anion X and a second halide anion X', at least one of the one or more initial precursor compounds comprises one of the first halide anion X and the second halide anion X', and at least one of the one or more additional precursor compounds comprises the other of the first halide anion X and the second halide anion X'.

[0186] In a more detailed example of the present invention, when [A] comprises a first monovalent cation A and a second monovalent cation A' and [X] comprises a first halide anion X and a second halide anion X', then the one or more initial precursor compounds may comprise one or more of the following:

[0187] i) an initial precursor compound comprising a first monovalent cation A and a first halide anion X (ie, AX);

[0188] ii) an initial precursor compound comprising a first monovalent cation A and a second halide anion X' (ie, AX');

[0189] iii) an initial precursor compound comprising a second monovalent cation A' and a first halide anion X (ie, A'X); and

[0190] iv) another precursor compound comprising a second monovalent cation A' and a second halide anion X' (ie, A'X').

[0191] Similarly, when [B] comprises / consists of a divalent inorganic cation B and [X] comprises a first halide anion X and a second halide anion X′, then the one or more further precursor compounds may comprise one or both of:

[0192] i) other precursor compounds comprising a divalent inorganic cation B and a first halide anion X (ie, BX2); and

[0193] ii) Other precursor compounds comprising a divalent inorganic cation B and a second halide anion X' (ie, BX'2).

[0194] Expanding on the two embodiments above, in a specific example, when the perovskite material comprises a single monovalent cation A, a single divalent inorganic cation B, and a single halide anion X, the initial precursor compound will generally include one of (i) a compound comprising a divalent inorganic cation B and a halide anion X and (ii) a compound comprising a monovalent cation A and a halide anion X. Other precursor compounds will include the other of (i) a compound comprising a divalent inorganic cation B and a halide anion X and (ii) a compound comprising a monovalent cation A and a halide anion X.

[0195] In this case, the compound comprising a divalent inorganic cation B and a halide anion X is a compound of the formula BX2, wherein B is a divalent inorganic cation and X is a halide anion; and the compound comprising a monovalent cation A and a halide anion X is a compound of the formula AX, wherein A is a monovalent cation and X is a halide anion.

[0196] If the monovalent cation A is an organic cation, the initial precursor compound preferably comprises a divalent inorganic cation B and a halide anion X, and the other precursor compounds will comprise a monovalent organic cation A and a halide anion X. Subsequently, if the monovalent cation A is an inorganic cation, the initial precursor compound may comprise one of (i) a compound comprising a divalent inorganic cation B and a halide anion X and (ii) a compound comprising a monovalent inorganic cation A and a halide anion X. The other precursor compounds will comprise the other of (i) a compound comprising a divalent inorganic cation B and a halide anion X and (ii) a compound comprising a monovalent inorganic cation A and a halide anion X.

[0197] In the above embodiment, the step of using vapor deposition to deposit a substantially continuous and conformal solid layer comprising one or more initial precursor compounds of the perovskite material on the rough surface may include using vapor deposition to deposit a substantially continuous and conformal solid layer comprising an inorganic material onto the rough surface, and subsequently treating the solid layer of the inorganic material with a gas of a halide X and thereby reacting the inorganic material and the halide to form a substantially continuous and conformal solid layer comprising the one or more initial precursor compounds on the rough surface.

[0198] This method can be used when each of the one or more initial precursor compounds comprises one of the one or more divalent inorganic cations [B]. The inorganic material deposited onto the rough surface using vapor deposition will then comprise inorganic material that forms the one or more divalent inorganic cations [B]. For example, when [B] comprises / consists of divalent inorganic cations B, the solid layer of inorganic material will comprise atoms that can form divalent inorganic cations B.

[0199] In a more specific example, when [B] contains a lead (II) cation (Pb 2+ ) / lead(II) cations (Pb 2+ ), the solid layer of inorganic material will include a solid layer of lead (Pb).

[0200] This method can also be used when the one or more monovalent cations [A] comprise one or more inorganic cations, and each of the one or more initial precursor compounds comprises one of the one or more monovalent inorganic cations. The inorganic material deposited onto the rough surface using vapor deposition will then comprise inorganic material that forms one or more monovalent inorganic cations. As an example, when [A] comprises / consists of a monovalent inorganic cation A, the solid layer of inorganic material will comprise atoms that can form a monovalent inorganic cation. In a more specific example, when [A] comprises a cesium cation (Cs + ) / Cesium cation (Cs +), the solid layer of inorganic material will include a solid layer of cesium (Cs).

[0201] The band gap of the perovskite material is preferably 1.10 eV to 2.30 eV, and preferably 1.65 eV to 1.75 eV.

[0202] As described above, the photovoltaic device may have a multi-junction structure comprising a first subcell disposed on a second subcell, the first subcell comprising a photoactive region comprising a perovskite material. In this case, the adjacent surface of the second subcell will have a roughness average value (R a ) or root mean square roughness (R rms ), and the roughened surface on which the perovskite material layer is disposed will conform to the roughened surface of the second subcell. For example, the roughened surface of the second subcell may include a surface within the second subcell having a surface texture. Such surface textures typically include one of pyramids and inverted pyramids.

[0203] The surface on which the solid layer of perovskite material is deposited may then be any one of an adjacent surface of the second subcell and an adjacent surface of a layer disposed between the solid layer of perovskite material and the second subcell and conforming to the rough surface of the second subcell.

[0204] The solid layer of perovskite material can be separated from the second subcell by one or more layers that each substantially conform to the rough surface of the second subcell. The one or more layers that separate the solid layer of perovskite material from the second subcell and that each substantially conform to the rough surface of the second subcell typically include a charge transport layer of the photosensitive region of the first subcell and any one of one or more interconnect layers disposed between and connecting the first and second subcells. The surface on which the solid layer of perovskite material is disposed includes an adjacent surface of the charge transport layer of the photosensitive region of the first subcell or an adjacent surface of the interconnect layer disposed between and connecting the first and second subcells.

[0205] The second subcell may include any of a second perovskite material, crystalline silicon, CdTe, CuZnSnSSe, CuZnSnS, or CuInGaSe (CIGS). Specifically, the second subcell may include a crystalline silicon subcell. Such a crystalline silicon subcell preferably includes a silicon heterojunction (SHJ), and more preferably, an amorphous silicon:crystalline silicon heterojunction. Alternatively, the second subcell may include a polycrystalline silicon subcell.

[0206] Figure 8a and Figure 8b An exemplary embodiment of the method of manufacturing a photovoltaic device as described above is schematically shown.

[0207] Figure 8a An exemplary embodiment is shown in which a substantially continuous and conformal solid layer of one or more initial precursor compounds comprising a perovskite material is deposited onto a rough surface by vapor deposition. In contrast, Figure 8b Exemplary embodiments are shown in which a substantially continuous and conformal solid layer comprising an inorganic material is deposited onto a rough surface by vapor deposition, and the layer comprising the inorganic material is subsequently treated with a halide gas to convert the inorganic material into a solid layer comprising one or more initial precursor compounds of the perovskite material.

[0208] exist Figure 8a In step (i), a second subcell 220 having a textured / rough top surface 221 is provided. In optional step (ii), an intermediate region 230 comprising one or more conformal interconnect layers can then be deposited onto the top surface 221 of the second subcell 220. In step (iii), one or more conformal layers of charge transport material (i.e., one or more n-type layers or p-type layers) are then deposited onto the top surface 221 of the second subcell 220 or (if present) the conformal intermediate region 230. In step (iv), a substantially continuous and conformal solid layer 114 of one or more initial precursor compounds comprising a perovskite material is deposited onto the rough surface by vapor deposition. In step (v), the solid layer 114 comprising one or more initial precursor compounds is then treated with one or more other precursor compounds that react together to form a substantially continuous and conformal solid layer of the perovskite material 113 on the rough surface 221.

[0209] exist Figure 8b In step (i), optional step (ii) and step (iii) Figure 8a Steps (i) to (iii) are the same as in Figure 8b In step (iv), a substantially continuous and conformal solid layer 115 comprising an inorganic material is deposited on the rough surface by vapor deposition. In step (v), the layer 115 comprising an inorganic material is then treated with a halide gas to convert the inorganic material into a solid layer 114 comprising one or more initial precursor compounds of the perovskite material. In step (vi), the solid layer 114 comprising one or more initial precursor compounds is then treated with one or more other precursor compounds that react together to form a substantially continuous and conformal solid layer of the perovskite material 113 on the rough surface 221.

[0210] exist Figure 8a and Figure 8bIn the embodiment of the present invention, the steps of treating the solid layer 114 comprising one or more initial precursor compounds (respectively steps (v) and (vi)) preferably comprise using solution deposition to treat the solid layer comprising one or more initial precursor compounds with a solution comprising one or more other precursor compounds. Alternatively, the steps of treating the solid layer 114 comprising one or more initial precursor compounds (respectively steps (v) and (vi)) comprise using vapor deposition to treat the solid layer comprising one or more initial precursor compounds with one or more other precursor compounds.

[0211] Example

[0212] Figure 9 is a plan view SEM image of a textured silicon substrate that has been coated with an ITO intermediate layer by sputtering and subsequently coated with a MAPbl of formula deposited on the conformal ITO layer using a typical spin coating solution process. 2.4 Br 0.6 (where MA is methylammonium). In the image, the light grey areas are areas of exposed ITO protruding through the perovskite material layer (shown in dark grey).

[0213] For comparison, Figure 10 This is a 45° SEM image of a textured silicon substrate that has been sputter-coated with an ITO interlayer and subsequently coated with a perovskite material layer of the formula MAPb13 (where MA is methylammonium) using the method described above. Specifically, the MAPb13 layer is produced by vapor deposition of a Pbl2 layer, followed by conversion by treatment with an MAI solution. As can be seen in this image, there are no areas of exposed ITO (absent light gray areas), and the perovskite material layer (shown in dark gray) has a surface profile that substantially conforms to that of the conformal ITO interlayer.

[0214] It should be understood that the above-mentioned items can be used alone or in combination with other items shown in the drawings or described in the specification, and items mentioned in the same paragraph or the same drawing do not need to be used in combination with each other.

[0215] In addition, although the present invention has been described in accordance with the preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only. Those skilled in the art will be able to make modifications and substitutions based on the disclosure that are contemplated to fall within the scope of the appended claims. For example, those skilled in the art will understand that although the above-mentioned specific embodiments of the present invention all relate to photovoltaic devices with multi-junction structures, various aspects of the present invention are equally applicable to single-junction devices in which a layer of photosensitive perovskite needs to be deposited onto a relatively rough surface. As another example, those skilled in the art will understand that although the above-mentioned embodiments of the present invention are all related to photovoltaic devices, various aspects of the present invention may also be applicable to other optoelectronic devices. In this regard, the term "photovoltaic device" includes photovoltaic devices, photodiodes (including solar cells), phototransistors, photomultipliers, photoresistors, and light-emitting diodes, etc. In particular, although in the above-mentioned embodiments, the photosensitive perovskite material is used as a light absorber / photosensitizer, it can also act as a light-emitting material by accepting charges (both electrons and holes) that are subsequently recombined and emit light. In addition, those skilled in the art will understand that although the above-mentioned embodiments of the present invention are all related to perovskite materials, various aspects of the present invention may also be applicable to other three-dimensional crystalline materials. As an example, various aspects of the present invention may also be applicable to perovskite-related structures, such as layered perovskites, brown iron structures (which may be represented by the general formula A 2+ 2B 3+ 2X 2- 5), a material having a barium manganite structure (which can be represented by the general formula A 2-y B 8-z Xi 16 Represented), spinel (which can be represented by the general formula A 2+ B 3+ 2X 2- 4), inverse spinel (which can be represented by formula B 3+ (A 2+ B 3+ )X 2- 4), olivine (which can be represented by formula A 2+ 2B 4+ X 2- 4 indicates) etc.

Claims

1. A multi-junction photovoltaic device comprising a first subcell disposed on a second subcell, the first subcell comprising a photosensitive region comprising a solid layer of a perovskite material, the perovskite material having the general formula [A][B][X]3, wherein [A] is at least one monovalent cation, [B] is at least one divalent inorganic cation, and [X] is at least one halide anion, wherein a surface of the second subcell adjacent to the first subcell has a roughness average value (R) greater than or equal to 50 nm. a ) or root mean square roughness (R rms ), and the solid layer of perovskite material is provided as a substantially continuous and conformal layer on a surface conforming to the rough surface of the second subcell, wherein The multi-junction photovoltaic device is manufactured using the following method, the method comprising: a) depositing a substantially continuous and conformal solid layer of one or more initial precursor compounds comprising the perovskite material on the roughened surface using vapor deposition, the one or more initial precursor compounds comprising one of: (i) a compound comprising a divalent inorganic cation B and a halide anion X, and (ii) a compound comprising a monovalent cation A and a halide anion X; and b) subsequently treating the solid layer comprising the one or more initial precursor compounds with one or more additional precursor compounds using solution deposition and thereby reacting the one or more initial precursor compounds and the one or more additional precursor compounds to form a dense, substantially continuous and conformal solid layer of the perovskite material on the rough surface, the one or more additional precursor compounds comprising another of: (i) a compound comprising a divalent inorganic cation B and a halide anion X, and (ii) a compound comprising a monovalent cation A and a halide anion X.

2. The multi-junction photovoltaic device of claim 1, wherein the rough surface of the second subcell adjacent to the first subcell comprises a surface within the second subcell provided with a surface texture, and the surface texture comprises one of a pyramid and an inverted pyramid.

3. A multi-junction photovoltaic device according to claim 1, wherein the surface on which the solid layer of perovskite material is disposed is any one of: an adjacent surface of the second sub-cell; and an adjacent surface of a layer disposed between the solid layer of perovskite material and the second sub-cell and conforming to the rough surface of the second sub-cell.

4. The multi-junction photovoltaic device of claim 3, wherein the solid layer of perovskite material is separated from the second subcell by one or more layers that each substantially conform to the roughened surface of the second subcell.

5. The multi-junction photovoltaic device of claim 4, wherein the one or more layers separating the solid layer of perovskite material from the second sub-cell and each substantially conforming to the roughened surface of the second sub-cell comprise any one of: a charge transport layer of the photosensitive region of the first subcell; and One or more interconnect layers are disposed between and connecting the first subcell and the second subcell.

6. The multi-junction photovoltaic device of claim 5, wherein the surface on which the solid layer of perovskite material is disposed comprises any one of: an adjacent surface of a charge transport layer of the photosensitive region of the first subcell; and Adjacent surfaces of an interconnect layer disposed between and connecting the first subcell and the second subcell. 7 . The multi-junction photovoltaic device of claim 1 , wherein the solid layer of perovskite material comprises a thin film of the perovskite material, and the thin film of the perovskite material has a thickness of 50 nm to 2 μm.

8. The multi-junction photovoltaic device of claim 7, wherein the thin film of the perovskite material has a thickness of 100 nm to 1000 nm.

9. The multi-junction photovoltaic device of claim 7, wherein the thin film of the perovskite material has a thickness of 200 nm to 700 nm.

10. The multi-junction photovoltaic device according to claim 1, wherein the rough surface of the second subcell has a roughness average value (R a ) or root mean square roughness (R rms ).

11. The multi-junction photovoltaic device according to claim 1 , wherein the rough surface of the second subcell has a roughness average value (R a ) or root mean square roughness (R rms ).

12. The multi-junction photovoltaic device according to claim 1, wherein the rough surface of the second subcell has a roughness average value (R a ) or root mean square roughness (R rms ).

13. The multi-junction photovoltaic device of claim 1, wherein the second subcell comprises any one of a second perovskite material, crystalline silicon, CdTe, CuZnSnSSe, CuZnSnS, or CuInGaSe (CIGS).

14. The multi-junction photovoltaic device of claim 7, wherein the second subcell comprises a crystalline silicon subcell, and the crystalline silicon subcell comprises a silicon heterojunction (SHJ).

15. The multi-junction photovoltaic device of claim 14, wherein the crystalline silicon subcell comprises an amorphous silicon:crystalline silicon heterojunction.

16. The multi-junction photovoltaic device of claim 1, wherein [X] comprises one or more halide anions selected from fluoride, chloride, bromide, and iodide.

17. The multi-junction photovoltaic device of claim 1, wherein [X] comprises one or more halide anions selected from chloride, bromide, and iodide.

18. The multi-junction photovoltaic device of claim 1, wherein [X] comprises one or more halide anions selected from bromide and iodide.

19. The multi-junction photovoltaic device of claim 1, wherein [X] comprises two different halide anions selected from fluoride, chloride, bromide, and iodide.

20. The multi-junction photovoltaic device of claim 1, wherein [X] comprises two different halide anions selected from chloride, bromide, and iodide.

21. The multi-junction photovoltaic device of claim 1, wherein [X] comprises bromide and iodide.

22. The multi-junction photovoltaic device of claim 1, wherein [A] comprises a compound selected from the group consisting of methylammonium (CH3NH3 + ), formamidine (HC(NH)2)2 + ) and ethylammonium (CH3CH2NH3 + ) at least one monovalent organic cation.

23. The multi-junction photovoltaic device of claim 1, wherein [B] comprises a compound selected from Pb 2+ and Sn 2+ at least one divalent inorganic cation.

24. The multi-junction photovoltaic device of claim 1, wherein [B] comprises Pb 2+ .

25. The multi-junction photovoltaic device of claim 1, wherein [A] comprises a + , Rb + 、Cu + 、Pd + , Pt + 、Ag + 、Au + , Rh + and Ru + One or more inorganic cations.

26. The multi-junction photovoltaic device of claim 1, wherein [A] comprises a + and Rb + One or more inorganic cations.

27. The multi-junction photovoltaic device of claim 1, wherein [A] comprises Cs + .

28. The multi-junction photovoltaic device of claim 1, wherein the band gap of the perovskite material is 1.10 eV to 2.30 eV.

29. The multi-junction photovoltaic device of claim 1, wherein the perovskite material has a band gap of 1.65 eV to 1.75 eV.

30. A multi-junction photovoltaic device according to claim 5, wherein the photosensitive region includes an n-type region having an n-type layer, a p-type region having a p-type layer, and a solid layer of perovskite material disposed between the n-type region and the p-type region, wherein the charge transport layer subsequently includes either the n-type layer of the n-type region or the p-type layer of the p-type region.

31. The multi-junction photovoltaic device of claim 1 , comprising: a first electrode and a second electrode, wherein the first subcell and the second subcell are disposed between the first electrode and the second electrode, wherein the first electrode is in contact with a p-type region of the first subcell, and the second electrode is in contact with the second subcell, wherein the first electrode comprises a transparent or semi-transparent conductive material, and the second electrode comprises a metal; or The first electrode contacts the n-type region of the first subcell, and the second electrode contacts the second subcell, wherein the first electrode comprises a transparent or semi-transparent conductive material, and the second electrode comprises a metal.

32. A multi-junction photovoltaic device comprising a photosensitive region having a layer of a perovskite material, the perovskite material having the general formula [A][B][X]3, wherein [A] is at least one monovalent cation, [B] is at least one divalent inorganic cation, and [X] is at least one halide anion, wherein the perovskite material layer is disposed on a substrate having a roughness average (R) greater than or equal to 50 nm. a ) or root mean square roughness (R rms ), the multi-junction photovoltaic device is manufactured using the following method, the method comprising: a) depositing a substantially continuous and conformal solid layer of one or more initial precursor compounds comprising the perovskite material on the rough surface using vapor deposition, the one or more initial precursor compounds comprising one of: (i) a compound comprising a divalent inorganic cation B and a halide anion X, and (ii) a compound comprising a monovalent cation A and a halide anion X; as well as b) subsequently treating the solid layer comprising the one or more initial precursor compounds with one or more additional precursor compounds using solution deposition and thereby reacting the one or more initial precursor compounds and the one or more additional precursor compounds to form a dense, substantially continuous and conformal solid layer of the perovskite material on the rough surface, the one or more additional precursor compounds comprising another of: (i) a compound comprising a divalent inorganic cation B and a halide anion X, and (ii) a compound comprising a monovalent cation A and a halide anion X.

33. A single-junction photovoltaic device comprising a transparent or semi-transparent front electrode and a back electrode, wherein a photosensitive region is disposed between the front electrode and the back electrode, wherein the photosensitive region comprises a perovskite material of formula (I): [A][B][X]3 (I) wherein [A] is at least one monovalent cation, [B] is at least one divalent inorganic cation, and [X] is at least one halide anion, in, The single-junction photovoltaic device is manufactured using the following method, the method comprising: a) using vapor deposition to deposit a substantially continuous and conformal solid layer comprising one or more initial precursor compounds of the perovskite material onto a substrate having a roughness average value (R a ) or root mean square roughness (R rms ), the one or more initial precursor compounds include one of the following: (i) a compound comprising a divalent inorganic cation B and a halide anion X, and (ii) a compound comprising a monovalent cation A and a halide anion X; and b) subsequently treating the solid layer comprising the one or more initial precursor compounds with one or more additional precursor compounds using solution deposition and thereby reacting the one or more initial precursor compounds and the one or more additional precursor compounds to form a dense, substantially continuous and conformal solid layer of the perovskite material on the rough surface, the one or more additional precursor compounds comprising another of: (i) a compound comprising a divalent inorganic cation B and a halide anion X, and (ii) a compound comprising a monovalent cation A and a halide anion X.

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