Paper
Paper
Although perovskite solar cells have made remarkable progress, the record device efficiency still lags far behind the theoretical limit efficiency. In this work, the ionic liquid, 1-ethyl-3-methylimidazolium chloride, is introduced into the triple-cation perovskite light absorption layer. The perovskite film with optimal amount of 1-ethyl-3-methylimidazolium chloride increases crystallinity, decreases pinholes and reduces defects density. As a result, the nonradiative recombination loss is efficiently restrained, accelerating the carrier extraction. The device modified with 1-ethyl-3-methylimidazolium chloride acquires a power conversion efficiency of 21.54%, which is considerably higher than that of the control device (18.12%). This work demonstrates that 1-ethyl-3-methylimidazolium chloride is a promising ionic liquid additive for high-performance perovskite solar cells.