The Importance of Moisture in Hybrid Lead Halide Perovskite Thin Film Fabrication
The Importance of Moisture in Hybrid Lead Halide Perovskite Thin Film Fabrication
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DOI：
10.1021/acsnano.5b03626
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发表时间：
2015-09-01
期刊：
影响因子：
17.1
通讯作者：
Snaith, Henry J.
中科院分区：
文献类型：
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作者：
Eperon, Giles E.;Habisreutinger, Severin N.;Snaith, Henry J.
湿度以环境湿度的形式对甲基铵卤化铅钙钛矿薄膜有显著影响。特别是，由于甲基铵组分的吸湿性，水分在成膜过程中起着重要的作用。到目前为止，这个问题还没有得到很好的理解，水分对所得薄膜的物理性质的影响也没有得到很好的理解。在这里，我们开展了一项全面的、可控的研究，研究了湿度暴露对甲基铵卤化铅钙钛矿薄膜的形成和性能的影响。我们发现，在较高湿度的空气中形成的薄膜具有较不连续的形貌，但显著提高了光致发光，并且成膜速度更快。在光伏器件中，我们发现在形成过程中暴露在湿气中，无论是在前体溶液中还是在大气中，都会显著提高开路电压，从而显著提高器件的整体性能。然后我们发现，通过对干膜进行湿暴露的后处理，我们可以以类似的方式提高光伏性能和光致发光。增强的光致发光和开路电压意味着暴露在潮湿中的薄膜的材料质量得到了改善。我们确定这种改善源于薄膜中陷阱密度的降低，我们假设这是由于部分挽救了甲铵组分和钙钛矿晶格的“自愈”。这项工作强调了在制造高性能钙钛矿器件时控制湿度暴露的重要性，并为制造的最佳环境提供了指导。此外，我们注意到，通常情况下，意外的水暴露可能是一些实验室生产的太阳能电池高性能的原因，而在干燥环境中仔细的合成和制造将导致性能较低的设备。
Moisture, in the form of ambient humidity, has a significant impact on methylammonium lead halide perovskite films. In particular, due to the hygroscopic nature of the methylammonium component, moisture plays a significant role during film formation. This issue has so far not been well understood and neither has the impact of moisture on the physical properties of resultant films. Herein, we carry out a comprehensive and well-controlled study of the effect of moisture exposure on methylammonium lead halide perovskite film formation and properties. We find that films formed in higher humidity atmospheres have a less continuous morphology but significantly improved photoluminescence, and that film formation is faster. In photovoltaic devices, we find that exposure to moisture, either in the precursor solution or in the atmosphere during formation, results in significantly improved open-circuit voltages and hence overall device performance. We then find that by post-treating dry films with moisture exposure, we can enhance photovoltaic performance and photoluminescence in a similar way. The enhanced photoluminescence and open-circuit voltage imply that the material quality is improved in films that have been exposed to moisture. We determine that this improvement stems from a reduction in trap density in the films, which we postulate to be due to the partial salvation of the methylammonium component and "self-healing" of the perovskite lattice. This work highlights the importance of controlled moisture exposure when fabricating high-performance perovskite devices and provides guidelines for the optimum environment for fabrication. Moreover, we note that often an unintentional water exposure is likely responsible for the high performance of solar cells produced in some laboratories, whereas careful synthesis and fabrication in a dry environment will lead to lower-performing devices.