Loss mechanisms in CZTS and CZTSe Kesterite thin-film solar cells: Understanding the complexity of defect density

Abstract Kesterite materials Cu2ZnSn(SxSe1−x)4, Cu2ZnSnS4 and Cu2ZnSnSe4 have received considerable attention as absorber layers for photovoltaic cell applications. But they exhibit efficiencies lower than 12%. In this work, different possible loss mechanisms that affect the solar cell performance are analysed. Numerical investigation is made on the influence of different loss mechanisms such as radiative recombination, presence of traps and defect densities on the performance of the device. A comparative between results on solar cells based on Cu2ZnSnS4 and Cu2ZnSnSe4 absorber layers is presented. The recombination mechanisms are found to play a vital role in degrading the performance of the solar cell. Additionally, trap centers and density of defect states are distributed to the absorber layer. It is observed that efficiency of the solar cell is severely affected and degraded by 10 % in the presence of defect states.