Ionic Liquid-Induced Multisite Synergistic Interactions for Highly Efficient Inverted Perovskite Solar Cells

The interfacial properties of p-i-n inverted perovskitesolar cells(PSCs) play a key role in further improving the photovoltaic performanceof PSCs. Herein, multisite synergistic interactions were constructedusing ionic liquids (ILs) prepared by mixing urea and choline chloride(ChCl) to substantially improve the interfacial properties of invertedPSCs. Systematically theoretical calculations and experimental studiesare comprehensively performed, which reveal that the C O & BULL;& BULL;& BULL;Pb2+ coordination interaction, N-H & BULL;& BULL;& BULL;Ihydrogen bond, and Cl-Pb bond could be simultaneously formedbetween the perovskites and IL, and Ch in IL could interact with theperovskite by occupying the formamidinium site. Meanwhile, -OH/& pi;and -NH/& pi; interactions could be formed between -OHand -NH in IL and the phenyl group in PTAA, respectively. Thesemultisite synergistic interactions are beneficial to improve the perovskitefilm quality and interfacial properties of inverted PSCs, which couldgreatly suppress nonradiative recombination within the PSCs. Consequently,the inverted PSCs show an impressive efficiency of 22.4% and an excellentelectroluminescence efficiency of 3.7%.