Zwitterionic Ionic Liquid Synergistically Induces Interfacial Dipole Formation and Traps State Passivation for High-Performance Perovskite Solar Cells

Defects at the interface and grain boundaries of perovskite solar cells (PSCs) will result in severe non -radiative recombination and open-circuit voltage (Voc) loss. Herein, we reported a zwitterionic ionic liq-uid imidazolium tetrafluoroborate (IMBF4) to passivate the defects at tin dioxide (SnO2)/perovskite inter-face. The results showed that the electron-rich nitrogen atom contained IM+ could diffuse into the buried perovskite to exhibit a strong chemical passivation effect on the organic vacancy defect by interacting with uncoordinated Pb2+. The F- in BF4- has a strong coordination effect with Pb2+in perovskite and Sn2+ in SnO2 synchronously to fill the anion vacancy defect. Also, the BF4 -anions could help to form an interface dipole layer to increase the charge transfer rate and reduce the work function. The IMBF4 mod-ified device could achieve an efficiency enhancement from 20.18% to 23.05% by vacuum flash-assisted solution-processed, with the increased Voc from 1.09 V to 1.15 V. The unencapsulated IMBF4 modified device could maintain 93% of the initial efficiency after ageing for 2000 h under ambient conditions by the ISOS-D-1 stability-testing protocols. This work emphasizes the importance of multifunctional additives in passivating defects and improving interface contact for achieving efficient and stable per-ovskite solar cells.(c) 2022 Elsevier Inc. All rights reserved.