CZTSe solar cells prepared by co-evaporation of multilayer Cu–Sn/Cu,Zn,Sn,Se/ZnSe/Cu,Zn,Sn,Se stacks

In this work, thin-film kesterite Cu2ZnSnSe4 (CZTSe) solar cells were prepared using a novel precursor configuration employing co-evaporated layer stacks of Mo/Cu–Sn/Cu,Zn,Sn,Se/ ZnSe/Cu,Zn,Sn,Se. It is found that this sequential deposition of the constituants leads to the formation of large CZTSe grains on the surface and fine grains at the Mo interface of the absorber, respectively. Prototype CZTSe solar cells using this stacked approach achieve power conversion efficiencies of up to 7.9% at an open-circuit voltage of 430 mV and a fill-factor of 62%. The analysis of temperature-dependent current density–voltage characteristics indicates that bulk Schottky–Read–Hall recombination is the dominant recombination mechanism for the devices fabricated from the proposed stack. In addition, the influence of pre-annealing of each stacked layer on the absorber growth and device performance is examined and discussed. Supplementary material for this article is available online