Ruddlesden-Popper reduced-dimensional hybrid perovskite (RDP) semiconductors have attracted significant attention recently due to their promising stability and excellent optoelectronic properties. Here, the RDP crystallization mechanism in real time from liquid precursors to the solid film is investigated, and how the phase transition kinetics influences phase purity, quantum well orientation, and photovoltaic performance is revealed. An important template-induced nucleation and growth of the desired (BA)(MA)PbI phase, which is achieved only via direct crystallization without formation of intermediate phases, is observed. As such, the thermodynamically preferred perpendicular crystal orientation and high phase purity are obtained. At low temperature, the formation of intermediate phases, including PbI crystals and solvate complexes, slows down intercalation of ions and increases nucleation barrier, leading to formation of multiple RDP phases and orientation randomness. These insights enable to obtain high quality (BA)(MA)PbI films with preferentially perpendicular quantum well orientation, high phase purity, smooth film surface, and improved optoelectronic properties. The resulting devices exhibit high power conversion efficiency of 12.17%. This work should help guide the perovskite community to better control Ruddlesden-Popper perovskite structure and further improve optoelectronic and solar cell devices.
|Original language||English (US)|
|State||Published - Apr 2 2018|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: X.Z., R.M., and Z.X. contributed equally to this work. This work was supported by the National Key Research and Development Program of China (2017YFA0204800, 2016YFA0202403), the National Natural Science Foundation of China (61604092, 61674098), the National University Research Fund (Grant Nos. GK261001009, GK201603055), the 111 Project (B14041), and the Chinese National 1000-talent-plan program (1110010341). GIWAXS measurements were performed at D-line in the Cornell High Energy Synchrotron Source (CHESS) and helped by the King Abdullah University of Science and Technology (KAUST). CHESS is supported by the NSF and the NIH/NIGMS via NSF award DMR-1332208.