Numerical simulation of the effect of gradual substitution of sulfur with selenium or tin with germanium in Cu2ZnSnS4 absorber layer on kesterite solar cell efficiency

To enhance the efficiency of kesterite Cu2ZnSnS4 solar cell, different gradient strategies are investigated. Absorber layer gradient is obtained by partial substitution of sulfur with selenium or tin with germanium. The PV Parameters are calculated using the SCAPS1D program. The effect of the front, back, and double gradient on the cell parameters was investigated. We proposed also the fully graded gap absorber layer profile. The opencircuit voltage has increased to 1.040V, the fill factor has increased to 71.69%, and the efficiency has exceeded 22.95%. In contrast to other types of gradients, the short-circuit current density remains high (Jsc= 39.7mA / cm2 ).