Cu₂ZnSnS₄ photovoltaic cell with improved efficiency fabricated by high‐temperature annealing after CdS buffer‐layer deposition

To improve the photovoltaic properties of Cu 2 ZnSnS 4 (CZTS) cells, we investigated the effect of both the thickness of the deposited CdS layers and the post‐annealing temperature following CdS deposition on the photovoltaic properties of CZTS cells using a two‐layer CZTS structure. By depositing a thin CdS layer (40 nm) followed by high temperature annealing (603 K), we observed a remarkable increase in the short‐circuit current density because of the enhancement of the external quantum efficiency in the wavelength range of 400–800 nm. The best CZTS cell exhibited a conversion efficiency of 9.4% in the active area (9.1% in the designated area). In addition, we also fabricated a CZTS cell with open‐circuit voltage of 0.80 V by appropriately tuning the composition of the CZTS layers.