Growth of large grain-size Cu2ZnSn(SxSe1-x)4 thin films by annealing precursors sputtered from a single quaternary target for solar cells application

A simple and cost effective method of sputtering a single quaternary target following a rapid thermal process (RTP) was applied to prepare Cu2ZnSn(SxSe1-x)4 (CZTSSe) thin films. The different Se supply during thermal annealing was used to adjust the Se contents in films. The structure, morphology, optical and electrical properties of the CZTSSe films were analyzed comprehensively. Polycrystalline kesterite CZTSSe absorbers with large columnar grains were obtained. The grains are densely packed and surfaces are smooth. The evolution of the optical and electrical properties with different Se contents in the CZTSSe films was studied in details. The conversion efficiency of the Se-rich CZTSSe thin film solar cell was determined to be 3.38%, and the corresponding J-V characteristic was analyzed carefully. The severe interface recombination is the key factor for the large ideality factor and reverse saturation current.