Loss mechanisms in hydrazine-processed $Cu2ZnSn(Se,S)4$ solar cells

We present a device characterization study for hydrazine-processed kesterite $Cu2ZnSn(Se,S)4$ (CZTSSe) solar cells with a focus on pinpointing the main loss mechanisms limiting device efficiency. Temperature-dependent study and time-resolved photoluminescence spectroscopy on these cells, in comparison to analogous studies on a reference $Cu(In,Ga)(Se,S)2$ (CIGS) cell, reveal strong recombination loss at the CZTSSe/CdS interface, very low minority-carrier lifetimes, and high series resistance that diverges at low temperature. These findings help identify the key areas for improvement of these CZTSSe cells in the quest for a high-performance indium- and tellurium-free solar cell.