Chitosan-Assisted Crystallization and Film Forming of Perovskite Crystals through Biomineralization

Graphical Crystal palace : Perovskite crystals with controlled morphology and properties are formed in a chitosan template by three steps including electrostatic adsorption/chelation, nucleation, and growth. The exposed functional groups of chitosan coordinate strongly with Pb 2+ and some of these stabilized Pb 2+ ions interact with I − ; nucleation occurs and perovskite crystals start to grow in the chitosan network. Biomimetic mineralization is a powerful approach for the synthesis of advanced composite materials with hierarchical organization and controlled structure. Herein, chitosan was introduced into a perovskite precursor solution as a biopolymer additive to control the crystallization and to improve the morphology and film-forming properties of a perovskite film by way of biomineralization. The biopolymer additive was able to control the size and morphology of the perovskite crystals and helped to form smooth films. The mechanism of chitosan-mediated nucleation and growth of the perovskite crystals was explored. As a possible application, the chitosan–perovskite composite film was introduced into a planar heterojunction solar cell and increased power conversion efficiency relative to that observed for the pristine perovskite film was achieved. The biomimetic mineralization method proposed in this study provides an alternative way of preparing perovskite crystals with well-controlled morphology and properties and extends the applications of perovskite crystals in photoelectronic fields, including planar-heterojunction solar cells.