Spatially Non-uniform Trap State Densities in Solution-Processed Hybrid Perovskite Thin Films

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• 作者：Sergiu Draguta ; Siddharatha Thakur ; Yurii V. Morozov ; Yuanxing Wang ; Joseph S. Manser ; Prashant V. Kamat ; Masaru Kuno
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2016
• 出版时间：February 18, 2016
• 年：2016
• 卷：7
• 期：4
• 页码：715-721
• 全文大小：439K
• ISSN：1948-7185

文摘

The facile solution-processability of methylammonium lead halide (CH₃NH₃PbI₃) perovskites has catalyzed the development of inexpensive, hybrid perovskite-based optoelectronics. It is apparent, though, that solution-processed CH₃NH₃PbI₃ films possess local emission heterogeneities, stemming from electronic disorder in the material. Herein we investigate the spatially resolved emission properties of CH₃NH₃PbI₃ thin films through detailed emission intensity versus excitation intensity measurements. These studies enable us to establish the existence of nonuniform trap density variations wherein regions of CH₃NH₃PbI₃ films exhibit effective free carrier recombination while others exhibit emission dynamics strongly influenced by the presence of trap states. Such trap density variations lead to spatially varying emission quantum yields and correspondingly impact the performance of both methylammonium lead halide perovskite solar cells and other hybrid perovskite-based devices. Of additional note is that the observed spatial extent of the optical disorder extends over length scales greater than that of underlying crystalline domains, suggesting the existence of other factors, beyond grain boundary-related nonradiative recombination channels, which lead to significant intrafilm optical heterogeneities.