Interface engineering with 1-Ethyl-3-methylimidazolium acetate for low-temperature-prepared mesoporous perovskite solar cells

The main challenge of applying low-temperature-prepared TiO 2 (LTP-TiO 2 ) to perovskite solar cells lies in its high density of defect states, which adversely affects electron transport at the interface and within the electron transport layer. Through strategic utilization of the ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIMAc), we developed an effective approach to passivate defect states of LTP-TiO 2 and enhance electron transport dynamics in perovskite photovoltaic devices. This ionic liquid additive simultaneously suppresses non-radiative recombination and improves electron extraction efficiency at the perovskite/TiO 2 interface. The EMIMAc-modified TiO 2 demonstrates an optimized electron mobility of 4.16×10 −5 cm²·υ⁻¹·s⁻¹, yielding a higher power conversion efficiency (PCE) of 21.03% with superior stability, thus marking a substantial enhancement over unmodified devices. Download: Download high-res image (212KB) Download: Download full-size image Ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIMAc) possesses an acetate anion that can strongly coordinate with under-coordinated Ti 4+ sites and passivate oxygen vacancies on the TiO 2 surface, while the imidazolium cation interacts with the perovskite to suppress interfacial defects. It can simultaneously suppress non-radiative recombination, improve charge extraction efficiency at the perovskite/TiO 2 interface and enhance the electron mobility of TiO 2 . A high efficiency of 21.03% with negligible hysteresis, improved stability was obtained when used low-temperature-processed TiO 2 as electron transport material in perovskite solar cells.