Lewis bases: promising additives for enhanced performance of perovskite solar cells

Lead halide perovskite is considered to be a very attractive photovoltaic material in the last few decades because of its rapid increase in efficiency. However, its instability under different environmental conditions and issues with its toxicity remain challenges. The approach of using multifunctional additives to increase the grain size, passivate both positively and negatively charged defects to enhance the long-term stability of perovskite has remained popular among the photovoltaic community. In this regard, a huge number of articles have been published in recent years focusing on additive engineering of perovskite. Here, we present a review on Lewis base additives in the precursor solution, anti-solvent, and interface treatment in perovskite to improve its photovoltaic properties. The grain boundaries are susceptible to decomposition because they have been found to carry the defects. To analyze the role of Lewis bases in increasing the grain size to minimize the grain boundary density in polycrystalline films for overall stability enhancement of perovskite, we detail the chelate effect and synergistic effect of additives in perovskite for solar cells. Finally, a future outlook is presented to discuss the critical challenges. Graphical abstract showing Lewis bases additives via different approaches to increase the stability of perovskite against ambient conditions of light, heat and humidity. [Display omitted] •High efficiency with increased stability is achieved by Lewis base additives in perovskite.•Lewis bases are effective passivating agents in perovskite solar cell materials.•Multidentate ligands control the crystallization in solution to avoid morphological defects due to the chelation.•Multifunctional Lewis bases enhance the grain size and cure the defects of perovskite.