Organic ionic plastic crystals: A promising additive for achieving efficient and stable CsPbI2Br perovskite solar cells

CsPbI2Br perovskite is a promising candidate for highly efficient photoactive materials. We firstly introduced an organic ionic plastic crystals additive, 1,1′-Spirobipyrrolidinium hexafluoride (SBP + PF6−), to increase the power conversion efficiency and improve the stability by adjusting the crystallization of the CsPbI2Br perovskite light-absorbing layer and passivating the pinhole defects at the grain boundary. The detailed results reveal that PF6− molecular anions can fill the vacancy in the X-site and passivate the interface defects. Moreover, SBP+ with high conductivity can be used to regulate A-site defects. The results show that the SBP + PF6− modified device exhibits a champion efficiency of 13.20%, enhanced by 19% than that of the control device. This work proposes not only a straightforward strategy to control the crystallization process in CsPbI2Br perovskite-based solar cells but also the functionality of organic ionic plastic crystals additive for chemical bonding and defects passivation to improve efficiency and stability.