Many reported CuIn1-xGaxSe2 (CIGS) thin films for high-efficiency solar cells have been prepared via a two-stage process that consists of a high-vacuum film deposition step followed by selenization with excess H2Se gas or Se vapor. Removing toxic gas and high-vacuum requirements from this process would greatly simplify it and make it less hazardous. We report the formation of CuIn1-xGaxSe2 (x = 0, 0.25, 0.50, 0.75, 1.0) thin films achieved by rapid thermal annealing of spray-deposited CuIn1-xGaxS2 and Se in the absence of an additional selenium source. To prepare the Se layer, commercial Se powder was dissolved by refluxing in ethylenediamine/2,2-dimethylimidizolidine. After cooling to room temperature, this mixture was combined with 2-propanol and the resulting colloidal Se suspension was sprayed by airbrush onto a heated glass substrate. The resulting film was coated with nanocrystalline CuIn1-xGaxS2 via spray deposition of a toluene-based “nanoink” suspension. The two-layer sample was annealed at 550 oC in an argon atmosphere for 60 minutes to form the final CIGS product. Scanning electron microscopy images reveal that film grains are 200–300 nm in diameter and comparable to sizes of the reactant CuIn1-xGaxS2 nanoparticles. XRD patterns are consistent with the chalcopyrite unit cell and calculated lattice parameters and A1 phonon frequencies change nearly linearly between those for CuInSe2 and CuGaSe2.

Many reported CuIn 1-x Ga x Se 2 (CIGS) thin films for high-efficiency solar cells have been prepared via a two-stage process that consists of a high-vacuum film deposition step followed by selenization with excess H 2 Se gas or Se vapor. Removing toxic gas and high-vacuum requirements from this process would greatly simplify it and make it less hazardous. We report the formation of CuIn 1-x Ga x Se 2 (x = 0, 0.25, 0.50, 0.75, 1.0) thin films achieved by rapid thermal annealing of spray-deposited CuIn 1-x Ga x S 2 and Se in the absence of an additional selenium source. To prepare the Se layer, commercial Se powder was dissolved by refluxing in ethylenediamine/2,2-dimethylimidizolidine. After cooling to room temperature, this mixture was combined with 2-propanol and the resulting colloidal Se suspension was sprayed by airbrush onto a heated glass substrate. The resulting film was coated with nanocrystalline CuIn 1-x Ga x S 2 via spray deposition of a toluene-based “nanoink” suspension. The two-layer sample was annealed at 550 o C in an argon atmosphere for 60 minutes to form the final CIGS product. Scanning electron microscopy images reveal that film grains are 200–300 nm in diameter and comparable to sizes of the reactant CuIn 1-x Ga x S 2 nanoparticles. XRD patterns are consistent with the chalcopyrite unit cell and calculated lattice parameters and A 1 phonon frequencies change nearly linearly between those for CuInSe 2 and CuGaSe 2 .

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A new room-temperature, aqueous solution-based preparation method for chalcopyrite CuInSe2 has been developed. Using 10% aqueous ethylenediamine as a solvent, the slow addition of Cu(NO3)2 to a mixture of indium(III) acetate, elemental Se, and sodium thioglycolate results in the formation of CuInSe2 as characterized by Raman spectroscopy. During this reaction, a kinetically-stable Cu2-xSe(s) intermediate initially forms followed by slow conversion to CuInSe2 that likely involves a direct Cu2-xSe + In2Se3 solid-state reaction. The ethylenediamine in the reaction mixture acts as a complexing agent, establishing equilibria that can be in competition with Cu2-xSe(s) formation, limiting particle size and accelerating rates of reaction with In. Over several hours, the CuInSe2 material undergoes a phase decomposition that can be reversed by annealing at 550 °C. Attempts to prepare CuIn1-xGaxSe2 and CuGaSe2 via this method result primarily in CuInSe2 and Cu2-xSe products, respectively, with nearly all gallium staying in the solution phase.

We report solvothermal preparations of nanocrystalline CuIn1-xAlxSe2 materials prepared from the reaction of Se, CuX2 (X = Cl− or stearate), InCl3, and Al(oleate)3 in refluxing oleylamine for 30 minutes to 3 hours. Scanning electron microscopy (SEM) images reveal morphologies consisting of hexagonal plates (100-400 nm diameter) with smaller isomorphic nodules. Micro-Raman spectroscopy, x-ray diffraction, and optical bandgap data are consistent with Al3+ incorporation into the chalcopyrite structure. For aluminum-containing reactions, product Al/(In+Al) ratios are estimated to be between 0.15 and 0.35 regardless of the indium-aluminum stoichiometry employed in the reaction. When Se is added to the reaction last, the reaction pathway involves an early-formed Cu2-xSe(s) intermediate that appears to react with In- and Al-containing species simultaneously. This intermediate is avoided when heating InCl3, Al(oleate)3, and Se together prior to Cu addition, but the final product includes Se contamination that must be removed or reacted by annealing.

We report solvothermal preparations of nanocrystalline CuIn 1-x Al x Se 2 materials prepared from the reaction of Se, CuX 2 (X = Cl − or stearate), InCl 3 , and Al(oleate) 3 in refluxing oleylamine for 30 minutes to 3 hours. Scanning electron microscopy (SEM) images reveal morphologies consisting of hexagonal plates (100-400 nm diameter) with smaller isomorphic nodules. Micro-Raman spectroscopy, x-ray diffraction, and optical bandgap data are consistent with Al 3+ incorporation into the chalcopyrite structure. For aluminum-containing reactions, product Al/(In+Al) ratios are estimated to be between 0.15 and 0.35 regardless of the indium-aluminum stoichiometry employed in the reaction. When Se is added to the reaction last, the reaction pathway involves an early-formed Cu 2-x Se(s) intermediate that appears to react with In- and Al-containing species simultaneously. This intermediate is avoided when heating InCl 3 , Al(oleate) 3 , and Se together prior to Cu addition, but the final product includes Se contamination that must be removed or reacted by annealing.