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In this study, SiOx layers were fabricated by spray pyrolysis deposition (SPD) and aerosol spraying as diffusion barriers between the stainless steel (SS) substrate (SUS430) and the molybdenum back contact layer in CuIn1-xGaxSe2 (CIGS) thin-film solar cells. SPD and aerosol spraying for SiOx layers are attractive processes for the deposition of thin films due to their low cost and controllable properties especially for solar cells on SS foils since a good barrier layer is required to prevent the Fe impurities (ions) defusing from SS substrate to the cells. The properties of SiOx barriers including thermal stability, microstructure content, electrical insulation and thickness of SiOx layers were investigated. The surface morphology and surface roughness were observed by scanning electron microscope and atomic force microscope. A transmission electron microscopy and X-ray diffractometer are adopted to measure the microstructural characteristics, grain size, and residual stresses of films. The chemical composition of the dielectric barriers was analyzed by X-ray photoelectron spectroscopy. The experimental results shows the specific thickness at 200 nm of SiOx layer will cause the absorber layer has the single chalcopyrite phase structure with (112) preferred orientation. The effects from the results revealed that the cells with a SiOx barrier layer fabricated by aerosol spraying provided a promising process in obtaining better CIGS cell performance.

Mixed alloy Cu–In–Ga precursors were deposited from Cu–Ga alloy and Indium targets by the DC magnetron co-sputtering method. There were four crystallization phases, In, CuIn 2 , Cu 11 In 9 and Cu 3 Ga, identified in the precursor after deposition. A large grain-size CIGS film was achieved by controlling the annealing period for selenization and utilizing a two-stage selenization process for secondary crystallization during rapid thermal annealing process. As the annealing temperature increased, the phase transitions moved toward the Cu-rich inter-metallic phases. In addition, the phase transition, stoichiometric ratio and surface-morphology were modified by Ar-ion plasma etching process of the precursors. The results show that after the ion etching process, the precursors can be transferred into a single Cu 11 In 9 crystallization phase and the number of crevices increased due to the soft texture of indium on the surface of the precursors. Finally, CIGS films with good crystalline properties were achieved after a suitable selenization process of only 1-stage.

In this study, the CuIn(Ga)Se2(CIGS) crystalline quality and MoSe2thickness of films produced by the rapid thermal selenization process under various selenization pressures were investigated. When the selenization pressure increased from 48 Pa to 1.45 × 104 Pa, the CIGS films were smooth and uniform with large crystals of varying sizes. However, the MoSe2thicknesses increased from 50 nm to 2,109 nm, which created increased contact resistivity for the CIGS/MoSe2/Mo structures. The efficiency of CIGS solar cells could be increased from 1.43% to 4.62% due to improvement in the CIGS crystalline quality with increasing selenization pressure from 48 Pa to 1.02 × 103 Pa. In addition, the CIGS crystalline quality and MoSe2thickness were modified by the pressure released valve (PRV) selenization process method. The crystalline qualities of the CIGS films were similarly affected by the selenization pressure at 1.02 × 103 Pa in the PRV selenization method and the MoSe2thicknesses were reduced from 1,219 nm to 703 nm. A higher efficiency of 5.2% was achieved with the thinner MoSe2obtained by using the PRV selenization method.

CIG precursors were deposited on the glass from the Cu-Ga alloy and Indium targets by co-sputtering method. The results show that when the sputtering pressure was increased, the surface morphology was changed from a roughness island-crystalline (RMS=165 nm) to a smaller pellet-crystalline (RMS=54.4 nm). At the same time the Cu/(In+Ga) ratio was increased. So, the crystallization of Cu11In9 phase was increasing and CuIn2 phase was decreasing in the CIG precursor. Then, a layer of selenium was coated on the precursor and the precursor was selenized using RTA selenization of 600 °C. The results show a good stoichiometric and crystallization under the parameters of the sputtering pressure at 4.2 mTorr of CIG precursors.