Li Dehui, Wang Gongming, Cheng Hung-Chieh, Chen Chih-Yen, Wu Hao, Liu Yuan, Huang Yu, Duan Xiangfeng
Department of Chemistry and Biochemistry, University of California, 607 Charles E. Young Drive East, Los Angeles, California 90095, USA.
California Nanosystems Institute, University of California, Los Angeles, California 90095, USA.
Nat Commun. 2016 Apr 21;7:11330. doi: 10.1038/ncomms11330.
Methylammonium lead iodide perovskite has attracted considerable recent interest for solution processable solar cells and other optoelectronic applications. The orthorhombic-to-tetragonal phase transition in perovskite can significantly alter its optical, electrical properties and impact the corresponding applications. Here, we report a systematic investigation of the size-dependent orthorhombic-to-tetragonal phase transition using a combined temperature-dependent optical, electrical transport and transmission electron microscopy study. Our studies of individual perovskite microplates with variable thicknesses demonstrate that the phase transition temperature decreases with reducing microplate thickness. The sudden decrease of mobility around phase transition temperature and the presence of hysteresis loops in the temperature-dependent mobility confirm that the orthorhombic-to-tetragonal phase transition is a first-order phase transition. Our findings offer significant fundamental insight on the temperature- and size-dependent structural, optical and charge transport properties of perovskite materials, and can greatly impact future exploration of novel electronic and optoelectronic devices from these materials.
甲基碘化铅钙钛矿最近在可溶液处理的太阳能电池及其他光电器件应用方面引起了广泛关注。钙钛矿中从正交相到四方相的相变会显著改变其光学和电学性质，并影响相应的应用。在此，我们通过结合变温光学、电输运和透射电子显微镜研究，对尺寸依赖的正交相到四方相的相变进行了系统研究。我们对不同厚度的单个钙钛矿微板的研究表明，相变温度随微板厚度的减小而降低。在相变温度附近迁移率的突然下降以及变温迁移率中滞后回线的存在证实了正交相到四方相的相变是一级相变。我们的研究结果为钙钛矿材料的温度和尺寸依赖的结构、光学和电荷输运性质提供了重要的基础见解，并可能极大地影响未来基于这些材料的新型电子和光电器件的探索。
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