Ligand-Assisted Breaking Crystal Symmetry to Achieve Stable γ-CsPbI<sub>3</sub> Nanorods with Strong Polarization Response
Wei Shen, Yujun Dai, Bo Cai, Shuo Chen, Shuo Chen, Hao Yang, Yangzhi Ma, Yanfeng Chen, Zhan Su, Jianbin Zhang, Yue Qiu, Yun Wang, Jiayu Jiang, Lihui Liu, Kun Cao, Shufen Chen, Shufen Chen
Abstract
Generally, the properties of CsPbX 3 (X = Cl, Br, I) are closely related to their morphology, size, composition and phase. Black phase (α, β, or γ) CsPbI 3 easily transforms to yellow phase (δ) CsPbI 3 accompanied by optical performance decay at room temperature. A temperature-dependent phase transition is a routine process for bulk CsPbI 3, whereas there is a lack of an effective method to control the phase of CsPbI 3 nanocrystals. It is still interesting and challenging to control the morphology and phase transition of black phase CsPbI 3 . Herein, we proposed a ligand-assisted strategy of breaking crystal symmetry via a short Pb–F bond to simultaneously achieve a phase transition and an nisotropic morphology. High-quality γ-CsPbI 3 nanorods (NRs) could be obtained due to F – preferential adsorption on the γ-CsPbI 3 (220) crystal plane to inhibit its growth and allow preferential growth orientation perpendicular to the γ-CsPbI 3 (202) crystal plane. Benefiting from Pb–F bond passivation and the hydrophobic phenyl group of ligands, γ-CsPbI 3 NRs exhibited good water resistance and crystal phase stability. Furthermore, a high-quality γ-CsPbI 3 NR film was assembled with a strong emission anisotropy polarization degree of up to 0.63 and the demo experiment of polarization imaging confirmed that the γ-CsPbI 3 NR film could meet the needs of practical applications.