Electron extraction mechanism in low hysteresis perovskite solar cells using single crystal TiO2 nanorods

Abstract

This study compares the photovoltaic performance of perovskite solar cells PSCs which use different types of TiO2 mesoporous scaffold; nanoparticle (NP) film and nanorod (NR) array. In PSCs of TiO2 NRs, the hysteresis of current density–voltage (J-V) curves is reduced significantly. The hysteresis index of PSCs of 670 nm long NRs is only 0.014. A difference in the charge accumulation at the TiO2-perovskite interface and the trapping site density is responsible for the smaller hysteresis of PSCs of TiO2 NRs. In PSCs of TiO2 NRs, mobile ions migrate longer and less electrons are trapped on the surface of TiO2 NRs. This leads to a unique columnar space charge polarization at the TiO2-perovskite interface, which facilitates electron extraction and suppresses the hysteresis of J-V curve. Our study shows a new way to design the microstructure of the mesoporous TiO2 layer for hysteresis-free high performance perovskite solar cells.