Spatial Localization of Excitons and Charge Carriers in Hybrid Perovskite Thin Films

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• 作者：Mary Jane Simpson ; Benjamin Doughty ; Bin Yang ; Kai Xiao ; Ying-Zhong Ma
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2015
• 出版时间：August 6, 2015
• 年：2015
• 卷：6
• 期：15
• 页码：3041-3047
• 全文大小：384K
• ISSN：1948-7185

文摘

The fundamental photophysics underlying the remarkably high-power conversion efficiency of organic鈥搃norganic hybrid perovskite-based solar cells has been increasingly studied using complementary spectroscopic techniques. However, the spatially heterogeneous polycrystalline morphology of the photoactive layers owing to the presence of distinct crystalline grains has been generally neglected in optical measurements; therefore, the reported results are typically averaged over hundreds or even thousands of such grains. Here we apply femtosecond transient absorption microscopy to spatially and temporally probe ultrafast electronic excited-state dynamics in pristine methylammonium lead tri-iodide (CH₃NH₃PbI₃) thin films and composite structures. We found that the electronic excited-state relaxation kinetics are extremely sensitive to the sample location probed, which was manifested by position-dependent decay time scales and transient signals. Analysis of transient absorption kinetics acquired at distinct spatial positions enabled us to identify contributions of excitons and free charge carriers.