Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02104—Forming layers
  • H01L21/02365—Forming inorganic semiconducting materials on a substrate
  • H01L21/02518—Deposited layers
  • H01L21/02521—Materials
  • H01L21/02568—Chalcogenide semiconducting materials not being oxides, e.g. ternary compounds
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02104—Forming layers
  • H01L21/02365—Forming inorganic semiconducting materials on a substrate
  • H01L21/02612—Formation types
  • H01L21/02617—Deposition types
  • H01L21/02623—Liquid deposition
  • H01L21/02628—Liquid deposition using solutions

Definitions

• the invention relates to a preparation process for thin semiconducting inorganic films comprising two or more metals (Cu/ln/Zn/Ga/Sn), selenium and/or sulfur.
• the process uses molecular metal-containing precursor complexes with organic S/Se/Te-containing ligands in combination with one or more precursors of a second metal which are free of S/Se/Te.
• Copper- based chalcopyrites of the l-lll-VI 2 -type are prepared with high purity at low temperatures in air or inert atmosphere.
• the thin films can be used in photovoltaic panels (solar cells).
• Photovoltaic panels are normally made of either crystalline silicon or thin-film cells. Many currently available solar cells are configured as bulk materials that are subsequently cut into wafers and treated in a "top-down" method of synthesis, with silicon being the most prevalent bulk material. In an attempt to make cheaper panels, other materials are configured as thin-films
• CISS and CIGS have a direct bandgap that is tunable by varying the In/Ga ratio or by varying the S/Se ratio to match the solar spectrum.
• Another advantage of CIGS is the lower environmental impact due to much lower cadmium content over the competing CdTe devices.
• Recently single-junction laboratory scale CIGS solar cells have been demonstrated to reach 19.9 % power conversion efficiency, higher than CdTe (16.5 %) or a-Si (12 %) based devices (I.
• the state of the art CIGS devices are made from vacuum processes such as the 3-stage co-evaporation of metals deposited under a selenium source in the chamber.
• the co-evaporation process poses difficulties in controlling film properties over large area substrates.
• the challenge involved in the vacuum process is the high control requirement for flux/deposition rate in order to avoid formation of intermediate compounds and to obtain controlled stoichiometry. Poor control of film properties over large area substrates adversely affects the device performance.
• Low material utilization of evaporated CIGS also increases costs as a part of the evaporated material ends up on the walls of the chamber.
• solution based processes are highly advantageous over the vacuum based as they can be used for roll-to-roll mass production with high throughput and significant cost reduction by close to 100 % material utilization.
• Solution based precursors can be used to deposit absorber layers by dip coating, spray coating, spin coating, slit coating, drop casting, doctor blading, ink-jet printing or flexographic/gravure printing etc.
• Spray pyrolysis is another solution based technique where metal salts like CuCI, InC , GaC with selenourea and their derivatives are dissolved in a solvent are sprayed on a hot substrate to produce CIS, CISS or CIGS films.
• metal salts like CuCI, InC , GaC with selenourea and their derivatives are dissolved in a solvent are sprayed on a hot substrate to produce CIS, CISS or CIGS films.
• This approach has resulted in low efficiencies due to unacceptably high impurity levels of C, CI and oxide phases (C. J. Hibberd Prog. Photovolt: Res. Appl., 2009; WO 8810513; JP 3068775A).
• the present invention uses and relates to a composition
• a composition comprising at least two different metal precursors and optionally a molecular or elemental chalcogen source that can be decomposed cleanly by heating without leaving any significant impurity content to form a semiconductor of the l-lll- Vl-type or related ones, and the incorporation into a working photovoltaic device as a thin film.
• a first metal precursor is a complex including an organic S/Se/Te-containing ligand, a second metal precursor is free of the elements S/Se/Te.
• the mixture is highly suitable for liquid phase processing with organic solvents.
• semiconductor comprising at least a first and a second metal, being different from each other and one or more elements chosen from S, Se or Te is presented, which is characterised in that
• one or more molecular precursor compounds comprising the first metal and at least one ligand (L) comprising one or more elements chosen from S, Se or Te
• the combined precursors are decomposed, preferably in an inert
• the preferred mode for decomposition of the precursors is by heating.
• chalcogen according to this invention is limited to sulfur (S), selenium (Se) and to some degree tellurium (Te).
• Selenium (Se), sulfur (S) and combinations of S and Se are preferred chalcogens, whereas
• the molecular precursor compound comprising the first metal and a ligand comprising one or more elements chosen from S, Se or Te is preferably a copper complex.
• the ligand comprising one or more elements chosen from S, Se or Te comprises preferably S or Se, and more preferably Se.
• the ligands are preferably organo-sulfur or organo-selenium compounds, more preferably thiourea, selenourea or derivates of these. Derivates of thiourea or selenourea are organic compounds where one or more of the hydrogen atoms are replaced by other groups found in organic compounds, especially groups as listed below in the definition of substituents R 1 to R 4 .
• the ligand comprising S or Se is described preferably by the following structure L:
• R 1 -R 4 Preferably at least two of R 1 -R 4 represent H. Beside hydrogen Ci -10 alkyl is preferred.
• At least one molecular precursor compound is preferably a metal complex of the structure
• M is Cu, In or Ga
• n 1 or 2
• n 1 to 8
• p 1 , 2, 3 or 4,
• x is 0, 0.5, 1 or 2
• L is a ligand of the formula L as described above,
• n, p, and x are chosen suitable for a metal-centered complex.
• One or more of the metals are employed as (S/Se/Te)-free precursors, which is preferably a metal complex comprising at least one ligand from the class of organic ligands bonding via an oxygen atom.
• oxygen ligands preferably include oximatos (for 2-oximato-carboxylates), ⁇ -diketonates, like e.g. acetylacetonates, carboxylates, like e.g. acetates and alkoxides, most preferably oximatos, which are all preferably free of halogenides.
• Typical metals which can be used as (S/Se/Te)-free complexes include copper, indium, gallium, zinc or tin, where indium or gallium are preferred.
• complexes of copper, indium or gallium with oximato ligands (2-hydroximinoalkanoates or 2-alkoximinoalkanoates) are used as precursors free of (S/Se/Te) for the film deposition method. More preferably indium and/or gallium oximato complexes are employed.
• Ligands of the oximato type preferably comprise a-2-(methoxyimino)alkanoate, 2-(ethoxyimino)alkanoate or 2-(hydroxyimino)alkanoate, more preferably the ethanoate, propanoate or butanoate within (C 2 - to Ce-) alkanoates, with the propanoates preferred most.
• oximato ligands (shorter: oximatos) according to the current invention is comprised by 2-oximino carboxylic acids, their derivates by variation of the residues (R 1 and R 2 ), and corresponding anions.
• a general structure of a preferred oximato ligand as referred to above and below is of the following formula:
• Ri is selected from H, CH 3 or CH 2 CH 3
• R 2 is selected from H, Ci to C6 alkyls, phenyl or benzyl, preferably H, CH 3 or CH 2 CH 3
• the oximato ligand usually is a chelate ligand with one negative charge. As a chelate ligand it bonds to the metal via the N and one of the O atoms.
• the oximato based metal precursors are stable in air and can be easily dissolved in common organic solvents such as methanol, ethanol, 2- methoxyethanol, DMF, DMSO etc.
• a synthesis using low levels of halogenides is applied, e.g. by exchanging the metal salts, often halogenides, into metal nitrates, sulfates, acetates or else.
• an oxocarboxylic acid preferably pyruvic acid
• an inorganic metal salt such as, for example, a nitrate
• the oximato ligands are synthesized by condensation of alpha- keto acids or oxocarboxylic acids with hydroxylamines or alkylhydroxyl- amines in the presence of bases in aqueous solution. Then, the metal precursors are formed at room temperature by addition of a metal salt, such as, for example, metal chloride or nitrate. Before using the metal complex as a precursor, it is isolated and cleaned in order to remove the residual ions and impurities.
• a metal salt such as, for example, metal chloride or nitrate.
• oxocarboxylic acids employed for making oximato ligands can be of varying chain length, but C2-C 6 carboxylic acids are preferred. Preference is given to the use of oxoacetic acid, oxopropionic acid (pyruvic acid) or oxobutyric acid.
• the semiconductors formed in the process according to the invention are of the I-III-VI 2 or I-II/IV-VI2 type and preferably of the l-lll-VI 2 type.
• the l-lll- Vl 2 type semiconductors one or more (+111) valency metals are used, preferably selected from In and Ga, more preferably In and In combined with Ga.
• the monovalent metal is preferably copper.
• the trivalent metals are preferably indium or gallium. Mixtures of these metals can be employed for tuning the band-gap of the semiconductor.
• the tervalent metal can be exchanged partly or completely against a mixture of divalent and tetravalent metals (l-ll/IV-V -type semiconductor, e.g. Cu(Zn/Sn)Se 2 , Cu(Zn/Ge)Se 2 ).
• Divalent metals are preferably cadmium or zinc, tetravalent metals are preferably germanium or tin.
• the precursors are preferably combined in a liquid phase, preferably a solvent providing good solubility of the components, and thus complete mixing of the metals with the chalcogen source is assured.
• the liquid phase preferably comprises an organic solvent or a mixture of two or more organic solvents.
• the solvent evaporates quickly when the mixture is applied to a substrate and heated to at least above the boiling point of the solvents. Accordingly, in step (b) of the process described above the decomposition is optionally preceded by the evaporation of any solvents.
• the environment for decomposition usually is inert gas, like nitrogen or argon.
• the precursors can also be decomposed in air.
• the precursor composition is preferably deposited on a substrate prior to decomposition, preferably by dip coating, spray coating, rod coating, spin coating, slit coating, drop casting, doctor blading, ink-jet printing or flexographic/gravure printing. Rapid evaporation and decomposition is preferred.
• the semiconductor is made by spray pyrolysis.
• the coating step is preferably repeated, intermitted or not by decomposition and /or heating of the material.
• Another aspect of the invention relates to a precursor composition for the formation of a semiconductor comprising at least a first and a second metal, being different from each other, and the semiconductor comprises further one or more elements chosen from S, Se or Te, where such precursor composition is a liquid solution or it is soluble in a suitable solvent or mixture of two or more solvents, characterized in that it comprises
• metal and a ligand comprising one or more elements chosen from S, Se and Te and
• iii) optionally a compound comprising S, Se or Te and not comprising a metal.
• precursors under points (ii) and (iii) are free from alkali and alkaline-earth metals or halogen (especially chloride).
• the precursor mixture preferably is a solution of the precursors in a liquid carrier.
• the molecular precursors are highly soluble materials, but the precursor mixture can also comprise additionally suspended small particles of additional compounds. In the inventive process no oxides are produced.
• the semiconductor materials consist of almost pure selenide/sulfide phases of the metals. The level of impurities of the elements O/C/N/CI is considerable lower than observed with methods according to prior art.
• the precursors are very stable in solution even at neutral conditions.
• alkali metal-free starting compounds are crucial for use in electronic components since residues containing alkali metals and alkaline- earth metals have an adverse effect on the electronic properties. These elements act as foreign atoms in the crystal and may have an unfavorable influence on the properties of the charge carriers.
• the precursor mixture consists of a liquid phase containing the precursor materials.
• the liquid phase can easily be processed by transferring it to surfaces to be covered with semiconducting material by spraying, dropping, dipping, printing etc.
• the liquid phase may preferably comprise organic solvents and solvent mixtures, more preferably solvents in which the precursors are soluble, mostly preferred polar-aprotic solvents like dimethylformamide (DMF), dimethyl sulfoxide (DMSO), etc and protic solvents like methanol, ethanol, 2-methoxyethanol, isopropanol etc.
• DMF dimethylformamide
• DMSO dimethyl sulfoxide
• protic solvents like methanol, ethanol, 2-methoxyethanol, isopropanol etc.
• Typical preferred precursors are for example described below.
• Preferred indium and gallium precursors are chosen from one or more of the structures according to Scheme 1 to 4 below.
• the substituents P ⁇ or R 2 can be chosen from H, CH 3 , C 2 H 5) etc and other organic groups.
• the gallium precursor has the same structure as the indium by exchanging the metal atom.
• the substituents R-i or R 2 can be chosen from H, CH 3 , C2H5, etc. and other organic groups, preferably groups as defined above for the oximato ligands.
• the gallium precursor has the same structure as the indium by exchanging the metal atom
• the substituents R 2 or R3 can be chosen from CH 3 , C2H5, etc. and other organic groups.
• the gallium precursor has the same structure as the indium by exchanging the metal atom.
• the substituents R can be chosen from H, CH 3l C 2 H 5 , etc. and other organic groups as defined as Ri above.
• the gallium precursor has the same structure as the indium by exchanging the metal atom.
• the thermal decomposition temperature of the precursor system according to the invention is as low as 150 °C and the end product after decomposition contains very low amounts of impurity elements like C or N ( ⁇ 1 %).
• the semiconductor layer typically has a thickness of 15 nm to 5 pm, preferably 30 nm to 2 m.
• the layer thickness is dependent on the coating technique used in each case and the parameters thereof. In the case of spin coating, these are, for example, the speed and duration of rotation. In the case of spraying, the thickness can be increased with spraying time. In the case of rod coating and doctor blading the thickness can be increased by repeated deposition steps.
• the substrate can be either a rigid substrate, such as glass, ceramic, metal or a plastic substrate, or a flexible substrate, in particular plastic film or metal foil.
• a rigid substrate such as glass, ceramic, metal or a plastic substrate
• a flexible substrate in particular plastic film or metal foil.
• molybdenum which is very effective for the performance of solar cells.
• the present invention furthermore relates to a process for the production of an electronic structure, preferably a device comprising a layered
• a photovoltaic device which is preferably a thin film photovoltaic or photoconducting device, characterized in that a) the precursor mixture according to the invention is applied to a
• Steps a) and b) can be performed concurrently by e.g. spraying on a hot substrate (spray pyrolysis). Repeating of step a) can be intermitted by one or more of steps b), which is preferred.
• the process produces semiconducting components and optionally the connections of the components in a electronic structure.
• the electronic structure can be part of a photovoltaic device, wherein the absorber layer comprises the produced semiconductor
• photovoltaic device is fabricated by depositing solvent precursor mixture according to the invention onto a substrate and thermally decomposing the precursors to obtain the semiconductor layer.
• solvent precursor mixture for example a copper- selenium precursor and an indium precursor are co-deposited and heated in an inert or air environment afterwards in order to obtain a CIS layer.
• the precursor mixture comprises relative amounts of the metal precursors which are equivalent to the stoichiometry of the desired semiconductor.
• the precursor mixture comprises relative amounts of the metal precursors which are equivalent to the stoichiometry of the desired semiconductor.
• the copper and indium precursor ratios can also be adjusted to make either slightly copper poor or copper rich CIS layer. Slightly copper poor CIS compositions have been shown in literature to have better photovoltaic performance.
• an additional compound comprising S, Se and/or Te and not comprising a metal is added into the process. It may be added at step a) by adding the compound to the combined precursors (the precursor composition) or during/after
• This optional source of S/Se Te which adds additional chalcogen, is preferably selected from organic compounds comprising selenium or sulphur or elemental selenium, sulphur or tellur, more preferably from selenourea/thiourea or their derivatives by exchanging hydrogen with other organic groups, thioacetamide, or elemental S/Se/Te dissolved or suspended as a powder in amines (like hydrazine,
• phosphines like tributylphosphine, trioctylphosphine, triphenylphosphine, etc.
• organic solvents like alcohols, DMF, DMSO etc.
• solvent mixtures of the aforementioned, or other suitable liquid carriers Sulphur and selenium are preferred chalcogens in this connection.
• the precursor mixture comprises an amount of the chalcogen component relative to the amount of metal which is equivalent to the stoichiometry of the desired semiconductor or more.
• an excess amount of the chalcogen can be used, because some of the selenium or sulfur may be lost due to the chalcogen volatility during annealing and decomposing the precursor mixture.
• the amount of chalcogen is preferably 100 %
• stoichiometric amounts of sulfur and additional selenium is included in the precursor comprising the first metal.
• the precursor mixture can be deposited on a "hot" substrate to decompose the precursor in-situ to form a semiconductor layer.
• This method practiced as spray pyrolysis, prevents crystallization of single species from the mixture prior to decomposition while the liquid carrier evaporates.
• the produced materials or layers may have a more homogeneous spatial distribution of the elements, but some additional surface roughness may be caused by spray deposition.
• Another method to produce the semiconductor material or the absorber layer is to deposit the precursor solution onto a substrate held at a temperature below the temperature of decomposition, typically at room temperature. This step is followed by annealing the films preferably in inert environment at the decomposition temperature of the precursors to convert the precursor films into a semiconductor layer, e.g. a CIS layer.
• An intermediate step can be the evaporation of the liquid carrier. This method provides more time to evenly distribute the precursor mixture in the required form or thickness onto a substrate.
• the precursor mixture is spray dried into hot inert gas providing a fine powder or grains of the semiconductor.
• the thermal conversion of the metal complex precursor into the functional semiconductor layer is carried out at a temperature > 150°C, preferably > 200 °C and more preferably > 300 °C.
• the temperature is preferably between 150 and 400°C.
• the residue after decomposition does not contain any significant carbon contamination ( ⁇ 1 %).
• the first decomposition step can be followed by further annealing steps to improve the electronic properties and crystallinity and/or grain size of the semiconductor, preferably the layer of semiconductor (more preferably CIS or CIGS layer).
• the grain size of the semiconductor film can be increased by increasing the annealing temperature and annealing time. No intermediate phases (which are detrimental to the PV performance) are formed if the precursors are completely decomposed.
• the process for the manufacture of a photovoltaic device according to the invention is free of any additional selenization and/or sulfurization step at temperatures above 250 °C. This way the temperatures in a process can be kept at 200 °C or lower.
• the inventive process according to the invention includes as a further step a selenization and/or sulfurization step and/or an annealing step after the decomposition of the precursors.
• the amount of chalcogen in the annealed films can be controlled by the initial chalcogen content in the precursor solution, by the amount and type of chalcogen present in the vapor phase and by the annealing/decomposition temperature and time.
• the conversion of the metal complex precursor or the precursor mixture into the functional semiconductor layer is carried out in a further preferred embodiment by irradiation, preferably electromagnetic irradiation, including microwaves, IR, and UV, with preference to UV light at wavelengths ⁇ 400 nm.
• the wavelength is preferably between 150 and 380 nm.
• the advantage of UV irradiation is that the layers produced thereby have lower surface roughness.
• the electronic component is provided with contacts to the semiconductor and completed in a conventional manner.
• a transparent top electrode made from e.g. ZnO or indium-tin oxide and a metal grid is provided.
• thioacetamide/lnC wash for band gap optimization and application of various contact layers (CdS, ZnO, ITO) may be employed to the
• the present invention furthermore relates to the use of the metal complex or precursor mixture according to the invention for the production of one or more functional layers, preferably the absorber layer, in a photovoltaic device.
• Copper selenourea precursors are listed where copper is complexed with thiourea or selenourea. The complexes were prepared following the references cited below. Copper selenourea precursors:
• the product comprises crystal water.
• Indium and gallium precursors Several indium and gallium precursors but not limited to following can be combined with copper binary precursors:
• Indium acetylacetonate tris[2-(methoxyimino)propanoato]indium (Indium oximato (J. Mater. Chem. 2010, 20, 8311 -8319), indium chloride, Indium acetylacetonate, indium acetate, indium methoxyethoxide, tris[2- (methoxyimino)propanoato]gallium (gallium oximato), gallium chloride, gallium acetate, gallium methoxyethoxide, etc.
• Metal-imino-complexes also referred to as oximato complexes, were prepared according to literature as compiled in e.g. WO 2012/000594 A1.
• Photovoltaic device with CIGS absorber made by spray coating copper thiourea precursor with other indium and gallium precursors from a solution.
• the precursor solution was made by dissolving Cu[(SC(NH 2 )2)4]CI-2H 2 O (0.2 mmol), tris[2-(methoxyimino)propanoato]indium (0.14 mmol, indium oximato complex, acc. to J. Mater. Chem. 2010, 20, 8311-8319) and gallium acetylacetonate (0.06 mmol) in 8 ml DMF.
• the clear precursor solution was spray coated at 20 psi pressure over 1" ⁇ 1" molybdenum coated glass substrate kept on a hot plate at 370 °C. The total spray volume was 4 ml per substrate for a total of 15 minutes.
• the CIGS film was transferred to a graphite box with a lid (not air tight) with a few selenium shots.
• the graphite box assembly was inserted in an argon filled quartz tube and heated in a tube furnace.
• the tube furnace was maintained at 550 °C and selenization is performed for 60 min.
• selenium pellets create selenium vapor over the substrate inside the enclosed graphite box and help to promote grain growth and higher crystallinity in the films.
• Figure 1 shows the x-ray diffraction pattern of sprayed and selenized films (after KCN etch).
• Figure 1 part (a) shows a broad peak (112) corresponding to a nanoparticulate grain size of the sprayed Culn x Ga( -x) S 2 film as well as a peak resulting from the molybdenum substrate. The average grain size of the sprayed film was calculated to be 5 nm by the Debye-Scherrer formula.
• the (112) peak position shifts to the left to lower 2 ⁇ values, showing a replacement of S by Se from the lattice leading to formation of Culn x Ga(i- x )Se 2 .
• the peak width also decreases significantly due to grain growth. Further smaller peaks such as (101), (211) appear showing chalcopyrite phase and higher crystallinity.
• Molybdenum selenide (MoSe 2 ) peaks can also be observed in Figure 1 part (b) due to reaction of
• molybdenum with selenium vapor during selenization The peak intensity for Mo is smaller after selenization showing that significant amount of the molybdenum is converted to molybdenum selenide.
• the film morphology and cross section of the selenized and KCN treated film were observed using scanning electron microscopy (SEM). Columnar grains were observed with grains growing over 2 ⁇ .
• the films were dipped in 10 wt% aqueous solution of KCN for 2 minutes and then rinsed in Dl water and dried under a stream of pressurized nitrogen.
• the KCN treatment is necessary to remove any copper selenide phase on the surface, that could be detrimental to the PV
• a CdS layer ⁇ 60 nm was deposited from a solution method described elsewhere (M.A. Contreras et al. Thin Solid Films 2002, 403-404, 204-211). ZnO (50 nm) and ITO (300 nm) thin films were deposited sequentially by RF sputtering. Next silver grids are hand-painted with commercially available silver paint on the devices. The silver paint covered about 15 % of the active device area (16.5 mm 2 ). The completed devices are annealed in air at 165 °C for 2 min to improve device performance.
• Figure 2 shows the photovoltaic device graphs with IV characteristics under dark and AM1.5 light condition.
• the above device characteristics are based on values without correction for the light blocked by silver grid area ( ⁇ 15 %).
• Photovoltaic device with CIGS absorber made by spray coating copper selenourea precursor with other indium and gallium precursors from a solution.
• a precursor stock solution was made by dissolving Cu(SeC(NH 2 )2)2CI
• the CIGS film was transferred to a graphite box with a lid (not air tight) with a few selenium shots.
• the graphite box assembly was inserted in a Argon filled quartz tube and heated in a tube furnace.
• the tube furnace was maintained at 550 °C and selenization is performed for 60 min.
• selenium pellets create selenium vapor over the substrate inside the enclosed graphite box and help to promote grain growth and higher crystallinity in the films.
• Figure 1 part (c) shows a broad peak (112) corresponding to a
• the average grain size of the sprayed film was calculated to be 7 nm by the Debye-Scherrer formula.
• Figure 1 part (d) shows that upon selenization the (112) peak width decreases significantly due to grain growth. Further smaller peaks such as (101), (211) appear showing chalcopyrite phase and higher crystallinity.
• Molybdenum selenide (MoSe 2 ) peaks can also be observed in Figure 1 part (d) due to reaction of molybdenum with selenium vapor during selenization. The peak intensity for Mo is smaller after selenization showing that significant amount of the molybdenum is converted to molybdenum selenide.
• the film morphology and cross section of the selenized and KCN treated film was observed using SEM. Partial grain growth occurred with few large and discrete grains (>0.5 - 2 ⁇ ) near the surface of the film. However most parts of the film had a well fused grainy microstructure with grains ⁇ 200 nm.
• a - 60 nm CdS film was deposited from a solution method described elsewhere (M.A. Contreras et al. Thin Solid Films 2002, 403-404, 204-211 ).
• ZnO (50 nm) and ITO (300 nm) thin films were deposited sequentially by RF sputtering.
• silver grids are hand-painted with commercially available silver paint on the devices. The silver paint covered about 15 % of the active device area (16.5 mm 2 ).
• the completed devices are annealed in air at 165 °C for 2 min to improve device performance.
• Figure 3 shows the photovoltaic device graphs with IV characteristics under dark and AM1.5 light condition.
• the above device characteristics are based on values without correction for the light blocked by silver grid area ( ⁇ 15 %).
• Photovoltaic device with CIGS absorber made by rod coating copper selenourea precursor with other indium and gallium precursors from a solution.
• a precursor stock solution was made by dissolving Cu(SeC(NH 2 ) 2 ) 2 CI (0.19 mmol), tris[2-(methoxyimino)propanoato]indium (indium oximato)
• the substrate was placed on a hot plate kept at 350 °C for 45 seconds to complete the conversion of precursor film to CIGS.
• the substrate was again transferred to the 120 °C hotplate and the rolling process was repeated to deposit the next layer followed by heating at 350 °C for 45 seconds. 15 such cycles were repeated to obtain a 1.2- 1.5 ⁇ thick film.
• the film was subjected to 45 min of annealing at 350 °C to remove any organics and to ensure complete conversion of the precursor layers to CIGS. All the above processing was done in a N 2 filled glove box with low levels of oxygen and moisture.
• the CIGS film was transferred to a graphite box with a lid (not air tight) with a few selenium shots.
• the graphite box assembly was inserted in a Argon filled quartz tube and heated in a tube furnace.
• the tube furnace was maintained at 550 °C and selenization is performed for 45 min.
• selenium pellets create selenium vapor over the substrate inside the enclosed graphite box and help to promote grain growth and higher crystallinity in the films.
• the films were dipped in 10 wt% aqueous solution of KCN for 2 minutes and then rinsed in Dl water and dried under a stream of pressurized nitrogen.
• the KCN treatment is necessary to remove any copper selenide phase on the surface, that could be detrimental to the PV
• Figure 4 shows the photovoltaic device graphs with IV characteristics under dark and AM1.5 light condition.
• the above device characteristics are based on values without correction for the light blocked by silver grid area (- 15 %).
• Smaller grains may provide higher number of defect sites that may act as recombination centers for charge carriers thereby resulting in lower efficiency values.
• Fig. 1 The graphs shows X-ray diffraction patterns (intensity plotted against diffraction angle 2 theta) of films according to the invention comprising (a, b) CIGS film according to device example 1 , and (c, d) CIGS film according to device example 2:
• Fig. 2 The graph shows the photovoltaic device response with IV
• Fig. 3 The graph shows the photovoltaic device response under dark and AM .5 light condition of CIGS solar cell described in device example 2.
• Fig. 4 The graph shows the photovoltaic device response under dark and AM1.5 light condition of CIGS solar cell described in device example 3.

Landscapes

• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Manufacturing & Machinery (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Photovoltaic Devices (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=48050658

Family Applications (1)

Country Status (2)

Cited By (1)

Citations (11)

• 2013
  • 2013-04-02 WO PCT/EP2013/000995 patent/WO2013159864A1/en active Application Filing
  • 2013-04-26 TW TW102114947A patent/TW201401344A/zh unknown

Patent Citations (11)

Non-Patent Citations (15)

Also Published As

Similar Documents

Legal Events