Impedance spectroscopy of Sb₂Se₃ photovoltaics consisting of (Sb₄Se₆)_n nanoribbons under light illumination

Sb2Se3, consisting of one-dimensional (Sb4Se6)(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 Sb2Se3 PVs. In this study, we investigated the charge carrier behavior in Sb2Se3 PVs by impedance spectroscopy (IS) under light illumination. (Sb4Se6)(n) nanoribbons with two different orientations were used to investigate the effect of crystal orientation on the device performance. Regardless of the (Sb4Se6)(n) orientation, negative capacitance was observed at forward bias, representing a recombination pathway at the TiO2/Sb2Se3 interface. A comparison of the recombination resistances and lifetimes of two different Sb2Se3 PVs showed that a better interface could be formed by placing the (Sb4Se6)(n) ribbons parallel to the TiO2 layer. Based on these observations, an ideal structure of the Sb2Se3/TiO2 interface is proposed, which will enhance the performance of Sb2Se3 PVs toward its theoretical limit.