A self-assembled molecule directs ordered α-FAPbI3 for n-i-p perovskite solar cells
Qingyun He, Junbo Wang, Mengyang Wu, Chongyu Zhong, Lei Li, Xiangru Zhao, Mengzhu Ding, Pinghui Yang, Renzhi Li, Wei Huang, Tianshi Qin, Fangfang Wang
Abstract
Formamidinium lead iodide (FAPbI3) perovskite is a leading candidate for high-efficiency solar cells, but its application is hindered by the kinetic instability of its α-phase crystallization. Here, a highly effective strategy for directing the ordered crystallization of α-FAPbI3 in the n-i-p architecture is developed by incorporating a self-assembled molecule (SAM) into the anti-solvent, unlike conventional phosphate-based SAMs requiring polar protic solvents, the -SCN SAM are processed from non-polar, aprotic solvents compatible with perovskite surfaces. An in-situ formed, self-assembled layer acts as a dynamic template, guiding the top-down crystallization process to yield highly ordered α-phase films. Through a series of in-situ measurements, it is rigorously demonstrated that this SAM treatment suppresses undesirable intermediate phases, accelerates the δ-to-α transition, and strategically slows crystal growth, promoting highly ordered films. This meticulously designed strategy culminates in high-quality perovskite films, enabling single-junction devices with a champion power conversion efficiency (PCE) of 26.18% (certified at 25.67%) and mini-modules with a PCE of 21.70%. These results underscore the power of directed self-assembly in fabricating highly efficient and stable n-i-p perovskite solar cells. Formamidinium lead iodide perovskite holds promise for high-efficiency solar cells, but the kinetic instability of its α-phase crystallization remains an issue. He et al. report a strategy for directing the crystallization process in a n-i-p architecture and champion power conversion efficiency of 26.18%.