Authors: Zhaotong Qin, Haibo Xue, Minchao Qin, Yuhao Li, Xiao Wu, Wei‐Ru Wu, Chun‐Jen Su, Geert Brocks, Shuxia Tao, Xinhui Lu
Published: 2023-01-02
Source: Full article
AbstractOrganic A′‐site ligand structure plays a crucial role in the crystal growth of 2D perovskites, but the underlying mechanism has not been adequately understood. This problem is tackled by studying the influence of two isomeric A′‐site ligands, linear‐shaped n‐butylammonium (n‐BA+) and branched iso‐butylammonium (iso‐BA+), on 2D perovskites from precursor to device, with a combination of in situ grazing‐incidence wide‐angle X‐ray scattering and density functional theory. It is found that branched iso‐BA+, due to the lower aggregation enthalpies, tends to form large‐size clusters in the precursor solution, which can act as pre‐nucleation sites to expedite the crystallization of vertically oriented 2D perovskites. Furthermore, iso‐BA+ is less likely to be incorporated into the MAPbI3 lattice than n‐BA+, suppressing the formation of unwanted multi‐oriented perovskites. These findings well explain the better device performance of 2D perovskite solar cells based on iso‐BA+ and elucidate the fundamental mechanism of ligand structural impact on 2D perovskite crystallization.