Multifunctional pi-Conjugated Additives for Halide Perovskite

Additive is a conventional way to enhance halide perovskite active layer performance in multiaspects. Among them, pi-conjugated molecules have significantly special influence on halide perovskite due to the superior electrical conductivity, rigidity property, and good planarity of pi-electrons. In particular, pi-conjugated additives usually have stronger interaction with halide perovskites. Therefore, they help with higher charge mobility and longer device lifetime compared with alkyl-based molecules. In this review, the detailed effect of conjugated molecules is discussed in the following parts: defect passivation, lattice orientation guidance, crystallization assistance, energy level rearrangement, and stability improvement. Meanwhile, the roles of conjugated ligands played in low-dimensional perovskite devices are summarized. This review gives an in-depth discussion about how conjugated molecules interact with halide perovskites, which may help understand the improved performance mechanism of perovskite device with pi-conjugated additives. It is expected that pi-conjugated organic additives for halide perovskites can provide unprecedented opportunities for the future improvement of perovskite devices.