Investigation of the Photovoltaic Properties of Cu2ZnSnS4 Solar Cell Considering the Relationship Between Defect and Hole

The thin film solar cell using chalcogenide Cu2ZnSnS4 (CZTS) absorber has exhibited promising photovoltaic performance in recent years. The carrier concentration of CZTS determines the built-in electric field and space-charge region that are important for the photo-generated carrier collections. Some simulated works studied the role of hole concentration of CZTS, but the defect concentration of CZTS is constant when the hole concentration is changed. In fact, the holes of an intrinsic CZTS originate from the anti-site and vacancy defects. In the present work, the influence of hole concentration of CZTS absorber on solar cell is calculated by simulation while the ratio of defect concentration to hole concentration is kept constant when the hole concentration is changed. When the ratio of defect concentration to hole concentration is low, the role of hole concentration is dominant. With the increase of hole concentration, the intensity of built-in electric field is enhanced, and the space-charge region becomes narrow. The optimal hole concentration is around ${1} \times 10^{{15}}$ – $1\times 10^{{17}}$ cm $^{-{3}}$ . For the high ratio of defect concentration to hole concentration case, the effect of defect should be considered. When the hole concentration of CZTS increases, the electric field of device weakens, leading to the inferior photovoltaic properties of device. Therefore, the defect concentration of CZTS should be reduced and the hole concentration needs to be increased to a suitable value for improving the properties of solar cell. This work gives a better understand of the photovoltaic mechanism of CZTS solar cell and provides guideline for future experimental work.