Organic halide salts and PbI2 in improving the efficiency of perovskite solar cells

First developed in 2012, perovskite solar cells (PSC) have been attracting enormous attention for their high-power conversion efficiency, low manufacturing cost, easy annealing and fabricating techniques, good stability in ambient environments, and excellent overall performance. Skyrocketing from a PCE of 2.8% to 25.2%, PSCs are deemed as one of the most promising solar energy harvesters in the near future. However, due to the grain boundaries and some poor interface connections, there appear several defects that affect the efficiency and stability of PSCs. In this case, two primary methods are discussed in this review to minimize such limitations: the introduction of (1) PbI2 and (2) organic halide salts as additives to the perovskite film. By filling the vacancies at the grain boundary, promoting spatial electron–hole separation, generating Lewis acid–base reaction, and forming intermolecular interactions like hydrogen bonding, sulfide bonds, pi-conjunctions, etc., these additives serve as promising candidates for reducing the surface recombination of PSCs. Moreover, because of the hydrophobic characteristics of organic halide-based compounds and the thermal annealing process, the stability of PSCs can also be improved in both high-temperature and -humidity environments. Through presenting and compiling the results of recent studies on various additives, this review also proposes further development and next-generation strategies for minimizing the limitations and challenges in the future