Spray-Pyrolyzed Three-Dimensional CuInS2 Solar Cells on Nanocrystalline-Titania Electrodes with Chemical-Bath-Deposited Inx(OH)ySz Buffer Layers

Three-dimensional (3D) compound solar cells with the structure of $\langle$Au/CuInS 2 /In x (OH) y S z /porous TiO 2 /compact TiO 2 /florin-doped tin-oxide-coated glass plates$\rangle$ have been fabricated by spray pyrolysis deposition of CuInS 2 and chemical-bath deposition of In x (OH) y S z for the light absorber and buffer layer, respectively. The effect of deposition and annealing conditions of In x (OH) y S z on the photovoltaic properties of 3D CuInS 2 solar cells was investigated. In x (OH) y S z annealed 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 In x (OH) y S z buffer 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 In x (OH) y S z buffer layers deposited for 1, 1.5, 1.75, and 2 h, that with In x (OH) y S z deposited for 1.75 h showed the best cell performance. The best cell performance was observed for In x (OH) y S z deposited for 1.75 h with annealing at 300 °C for 30 min in air ambient, and cell parameters were 22 mA cm -2 short-circuit photocurrent density, 0.41 V open-circuit voltage, 0.35 fill factor, and 3.2% conversion efficiency.