CZTS BASED THIN FILM SOLAR CELL: : An Investigation into the Influence of Dark Current on Cell Performance

CZTS thin films are relatively inexpensive and so could help to improve the cost-effectiveness of solar technology. In this work, the effects of various components of the dark current are investigated. A detailed mathematical model of the current density-voltage relationship of n-CdS/p-CZTS solar cell under illumination is used for this purpose. The following dark current components are considered in the analysis: diffusion, trap-assisted tunneling recombination, thermionic emission, radiative recombination, and CdS/CZTS interface recombination. It is found that trap-assisted tunneling recombination, CdS/CZTS interface recombination and thermionic emission have the greatest effect while the effects of diffusion and radiative recombination are negligible. In addition, it is found that the significance of the largest dark current component changes as donor and acceptor concentrations are altered. Using these results, the optimum values for donor and acceptor concentration of 10¹⁸ and 5*10¹⁴ cm^-3, respectively, with CdS thickness of 50 nm and CZTS thickness 5 μm have been determined for the maximum efficiency of 14.4% for CdS/CZTS solar cell.