Potential buffer layers for Cu2ZnSnS4 (CZTS) solar cells from numerical analysis

Recently Cu₂ZnSnS₄ (CZTS) absorber layer research shows extensive influential factors to replace expensive CIGS absorber layer. In this work, potential buffer layers for CZTS solar cells like ZnO, ZnS, ZnSe, and InS as replacement to conventional CdS buffer layer are numerically analysed. Among all the used structures, ZnS/ CZTS structure shows an optimum efficiency of 13.71 % (with V_oc= 0.78 V, J_sc= 31.97 mA/cm², and fill factor = 55 %). This work explicitly reveals the most favorable CZTS layer thickness in the range of 1 μm to 2.2 μm, whereas buffer layer thickness lies down between 50 nm and 80 nm. It is not trivial to achieve promising efficiency for ZnO/CZTS structure as well. Temperature effects on the cells are also observed. The efficiency of ZnS/CZTS solar cells downsized from 13.71% (300k) to around 11.07% (350 K) with an absolute decreasing rate of -dη/dT(%k^-1) = 0.05 whereas -dη/dT(%k^-1) = 0.03 for ZnO/CZTS cell. Also, cells ideality is determined by theoretical modeling. The achieved results can lead to develop higher efficiency CZTS thin film solar cells.