Performance enhancement of Cu2ZnSn(S, Se)4 solar cells by post-selenization of absorber layer in thermal-cracked selenium atmosphere

Abstract

Self-designed selenium thermal-cracking system is used to produce selenium vapor with high activity for sufficient selenization of CZTSSe absorber. CZTS precursor film prepared by magnetron sputtering of CZTS quaternary target. By adjusting the heating temperature of selenium source to 600 °C, macromolecular Sen can be cracked to small molecule Sen with high reaction activity, which is helpful to form densely packed large grains in the CZTSSe absorber due to the reduction of selenium vacancies and the enhancement of surface migration. The crystallization quality of CZTSSe absorber is further improved by the optimization of selenium source heating rate. A peak performance of solar cells achieved exhibiting a power conversion efficiency of 7.9%, with Voc of 410 mV, Jsc of 35.25 mA/cm2 and FF of 54.98%. J-V characterization, electrochemical impedance spectra and capacitance-voltage tests are also employed to analysis the device performance enhancement mechanism.