Spray-Pyrolyzed Three-Dimensional CuInS2Solar Cells on Nanocrystalline-Titania Electrodes with Chemical-Bath-Deposited Inx(OH)ySzBuffer Layers

Three-dimensional (3D) compound solar cells with the structure of 2/Inx(OH)ySz/porous TiO2/compact TiO2/florin-doped tin-oxide-coated glass plates> have been fabricated by spray pyrolysis deposition of CuInS2and chemical-bath deposition of Inx(OH)ySzfor the light absorber and buffer layer, respectively. The effect of deposition and annealing conditions of Inx(OH)ySzon the photovoltaic properties of 3D CuInS2solar cells was investigated. Inx(OH)ySzannealed in air ambient showed a better cell performance than those annealed in nitrogen ambient and without annealing. The improvement of the performance of cells with Inx(OH)ySzbuffer layers annealed in air ambient is due to the increase in oxide concentration in the buffer layers [confirmed by X-ray photoelectron spectroscopy (XPS) measurement]. Among cells with Inx(OH)ySzbuffer layers deposited for 1, 1.5, 1.75, and 2 h, that with Inx(OH)ySzdeposited for 1.75 h showed the best cell performance. The best cell performance was observed for Inx(OH)ySzdeposited for 1.75 h with annealing at 300 °C for 30 min in air ambient, and cell parameters were 22 mA cm-2short-circuit photocurrent density, 0.41 V open-circuit voltage, 0.35 fill factor, and 3.2% conversion efficiency.