Impedance spectroscopy of Sb ₂ Se ₃ photovoltaics consisting of (Sb ₄ Se ₆ ) _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.