Effect of crystal growth rate on crystal direction, defect formation, and photovoltaic performance of Sb2Se3 thin-film solar cells

Abstract

This study investigates the effect of the crystal growth rate, which is controlled via temperature ramping during the selenization process, on the crystal direction, defect formation, and photovoltaic performance of antimony triselenide (Sb2Se3) thin-film solar cells. Sb2Se3 absorbers are fabricated through sputtering-based Sb deposition followed by post-selenization at ramping rates of 40 and 60 degrees C min-1. Faster temperature ramping (60 degrees C min-1) promotes rapid grain growth, yielding a dominant [002] and [hkl] (l not equal 0) crystal direction, which enhances the carrier transport along the (Sb4Se6)n ribbons. This preferential direction reduces the defect density and improves key device metrics, including the photovoltaic conversion efficiency, open-circuit voltage, current density, fill factor, and carrier lifetime. In contrast, slower ramping (40 degrees C min-1) yields a more random crystal direction and higher defect density, adversely affecting the device performance. Comprehensive characterization via SEM, XRD, UPS, admittance spectroscopy, and STEM-EDS supports these findings and reveals that variations in the Se/Sb ratio influence the defect formation. The proposed carrier transport model indicates that crystal growth dynamics optimization is a promising strategy for Sb2Se3 solar-cell performance enhancement.