Abstract
Sb$_2$Se$_3$, consisting of one-dimensional (Sb$_4$Se$_6$)$_n$ nanoribbons has drawn attention as an intriguing light absorber from the photovoltaics (PVs) research community. However, further research is required on the performance-limiting factors in Sb$_2$Se$_3$ PVs. In this study, we investigated the charge carrier behavior in Sb$_2$Se$_3$ PVs by impedance spectroscopy (IS) under light illumination. (Sb$_4$Se$_6$)$_n$ nanoribbons with two different orientations were used to investigate the effect of crystal orientation on the device performance. Regardless of the (Sb$_4$Se$_6$)$_n$ orientation, negative capacitance was observed at forward bias, representing a recombination pathway at the TiO$_2$/Sb$_2$Se$_3$ interface. A comparison of the recombination resistances and lifetimes of two different Sb$_2$Se$_3$ PVs showed that a better interface could be formed by placing the (Sb$_4$Se$_6$)$_n$ ribbons parallel to the TiO$_2$ layer. Based on these observations, an ideal structure of the Sb$_2$Se$_3$/TiO$_2$ interface is proposed, which will enhance the performance of Sb$_2$Se$_3$ PVs toward its theoretical limit.
Park, Jaemin