Electric dipole moment-assisted charge extraction and effective defect passivation in perovskite solar cells by depositing a PCBM:TIPD blend film on a CH3NH3PbI3 layer

Abstract

Simultaneously increasing the charge extraction efficiency from a perovskite layer and reducing the defect states in perovskite crystals are critical to the performance and stability of perovskite solar cells (PSCs). For this purpose, the PCBM:TIPD-blended CBZ hybrid anti-solvent method is used for the first time to deposit a PCBM:TIPD blended film on a CH₃NH₃PbI₃ layer for PEDOT:PSS_PH1000-based PSCs. The PCBM and TIPD fill up the voids and pinholes on the perovskite surfaces and thus produces more compact and pinhole-free perovskite films. Compared to just using Clevios PVP AI 4083 and PCBM, the simultaneous use of PEDOT:PSS_PH1000 and PCBM:TIPD is more conducive to the extraction and separation of photo-generated charges from the perovskite. First-principles calculations show that the TIPD aligns the organic molecules of methylammonium in the same direction, and thus produces electric dipole moments and electric fields at the TIPD/perovskite interface, which promotes the electron transfer from the perovskite to the PCBM and TIPD more efficiently. Moreover, the TIPD can effectively reduce the defect states caused by under-coordinated Pb ions. As a result, the performance and stability of the PSCs treated with the PCBM and TIPD are also significantly improved. The highest efficiency of 15.2% is achieved by the cell with PCBM:TIPD-blended CBZ anti-solvent treatment, which presents a 45% improvement compared to that of 10.5% for the PSCs with pure CBZ anti-solvent treatment.