Enhanced performance of planar perovskite solar cells based on low-temperature processed TiO2 electron transport layer modified by Li2SiO3

Planar perovskite solar cells based on Li2SiO3 modified TiO2 electron transport layer are fabricated by one-step method. Here the Li2SiO3 modified TiO2 films are prepared by a simple soaking process at 65 °C. The effect of Li2SiO3 modification on the photoelectric properties of TiO2 films and devices has been systematically investigated. Compared to the reference TiO2, the modified TiO2 demonstrates better characteristics such as better surface wetting properties of perovskite precursor, enhanced electron mobility and reduced electron trap state density, which contribute to the favorable photovoltaic performance. At the optimized process, the device based on the modified TiO2 film yields a champion power conversion efficiency of 18.67%, being much higher than 14.78% of the reference device. The improved performance is primarily attributed to the promoted charge transport and reduced charge recombination in the modified electron transport layer. This work provides a simple route to obtain efficient planar perovskite solar cells by low-temperature process, which will be compatible with flexible plastic substrates in future practical applications.