π-Conjugated Zwitterion for Dual-Interfacial Modification in High-Performance Perovskite Solar Cells

Abstract Interfacial modification of perovskite solar cells (PSCs) with solution-processed zwitterionic materials is an attractive approach to improving device efficiency and stability. However, zwitterionic molecules for multifunctional modification in PSCs have been rarely reported. In this work, a zwitterionic unit is introduced as an acceptor group in a new n-type π-conjugated zwitterion, IT-IN. This newly developed interfacial material can not only act as a high-quality electron transport layers (ETLs) but also enable effective defect passivation of a perovskite film, to reduce the trap densities inside it. By incorporating IT-IN between Ag cathode and PC61BM to constitute a bilayer ETLs, a significant improvement in power conversion efficiency (PCE) of inverted PSCs from 16.68% to 19.60% is achieved. Furthermore, after introducing IT-IN into perovskite films as passivation agent, the PCE of the PSCs is further enhanced to 21.24%. In addition, our fabricated PSCs exhibit excellent stability in air because of the dual-interfacial modification. This work provides new insights on the design and application of multifunctional interface material for efficient and low-cost PSCs.