Nucleation and Crystal Growth of Organic-Inorganic Lead Halide Perovskites under Different Relative Humidity
Nucleation and Crystal Growth of Organic-Inorganic Lead Halide Perovskites under Different Relative Humidity
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不同相对湿度下有机-无机卤化铅钙钛矿的成核与晶体生长
DOI：
10.1021/acsami.5b00895
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发表时间：
2015-05-06
影响因子：
9.5
通讯作者：
Zou, Zhigang
中科院分区：
文献类型：
--
作者：
Gao, Hao;Ban, Chunxiong;Zou, Zhigang
有机-无机卤化铅钙钛矿化合物是非常有前途的高效钙钛矿太阳能电池材料。但由于钙钛矿薄膜对水分的敏感性，如何在受控湿度条件下制备高质量的钙钛矿薄膜仍然是一个重要问题。在这项研究中，我们研究了环境湿度对一步旋涂钙钛矿薄膜的结晶和表面形貌的影响，以及基于这些钙钛矿薄膜的太阳能电池的性能。基于实验分析和薄膜生长理论，我们得出结论，环境湿度对旋涂阶段成核的影响与退火阶段晶体生长的影响有很大不同。在旋涂阶段，高过饱和度引起的高成核密度更倾向于在无水环境下出现，从而导致钙钛矿薄膜的层生长和高覆盖率。但在退火阶段，适度的过饱和度有利于形成具有良好结晶度的钙钛矿薄膜。在低相对湿度 (RH) 下旋涂并随后在高相对湿度 (RH) 下退火的薄膜显示出结晶度的增加和器件性能的改善。因此，在高质量钙钛矿薄膜的形成过程中，提出了一种快速成核随后适度晶体生长的机制（旋涂阶段的高过饱和度和退火阶段的适度过饱和度）。
Organic-inorganic lead halide perovskite compounds are very promising materials for high-efficiency perovskite solar cells. But how to fabricate high-quality perovksite films under controlled humidity conditions is still an important issue due to their sensitivity to moisture. In this study, we investigated the influence of ambient humidity on crystallization and surface morphology of one-step spin-coated perovskite films, as well as the performance of solar cells based on these perovskite films. On the basis of experimental analyses and thin film growth theory, we conclude that the influence of ambient humidity on nucleation at spin-coating stage is quite different from that on crystal growth at annealing stage. At the spin-coating stage, high nucleation density induced by high supersaturation prefers to appear under anhydrous circumstances, resulting in layer growth and high coverage of perovskite films. But at the annealing stage, the modest supersaturation benefits formation of perovskite films with good crystallinity. The films spin-coated under low relative humidity (RH) followed by annealing under high RH show an increase of crystallinity and improved performance of devices. Therefore, a mechanism of fast nucleation followed by modest crystal growth (high supersaturation at spin-coating stage and modest supersaturation at annealing stage) is suggested in the formation of high-quality perovskite films.