Tunable hysteresis effect for perovskite solar cells

Abstract

Perovskite solar cells (PSCs) usually suffer from a hysteresis effect in current–voltage measurements, which leads to an inaccurate estimation of the device efficiency. Although ion migration, charge trapping/detrapping, and accumulation have been proposed as a basis for the hysteresis, the origin of the hysteresis has not been apparently unraveled. Herein we reported a tunable hysteresis effect based uniquely on open-circuit voltage variations in printable mesoscopic PSCs with a simplified triple-layer TiO₂/ZrO₂/carbon architecture. The electrons are collected by the compact TiO₂/mesoporous TiO₂ (c-TiO₂/mp-TiO₂) bilayer, and the holes are collected by the carbon layer. By adjusting the spray deposition cycles for the c-TiO₂ layer and UV-ozone treatment, we achieved hysteresis-normal, hysteresis-free, and hysteresis-inverted PSCs. Such unique trends of tunable hysteresis are analyzed by considering the polarization of the TiO₂/perovskite interface, which can accumulate positive charges reversibly. Successfully tuning of the hysteresis effect clarifies the critical importance of the c-TiO₂/perovskite interface in controlling the hysteretic trends observed, providing important insights towards the understanding of this rapidly developing photovoltaic technology.