Imaging Electronic Trap States in Perovskite Thin Films with Combined Fluorescence and Femtosecond Transient Absorption Microscopy

详细信息    查看全文

• 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：2016
• 出版时间：May 5, 2016
• 年：2016
• 卷：7
• 期：9
• 页码：1725-1731
• 全文大小：456K
• 年卷期：0
• ISSN：1948-7185

文摘

Charge carrier trapping degrades the performance of organometallic halide perovskite solar cells. To characterize the locations of electronic trap states in a heterogeneous photoactive layer, a spatially resolved approach is essential. Here, we report a comparative study on methylammonium lead tri-iodide perovskite thin films subject to different thermal annealing times using a combined photoluminescence (PL) and femtosecond transient absorption microscopy (TAM) approach to spatially map trap states. This approach coregisters the initially populated electronic excited states with the regions that recombine radiatively. Although the TAM images are relatively homogeneous for both samples, the corresponding PL images are highly structured. The remarkable variation in the PL intensities as compared to transient absorption signal amplitude suggests spatially dependent PL quantum efficiency, indicative of trapping events. Detailed analysis enables identification of two trapping regimes: a densely packed trapping region and a sparse trapping area that appear as unique spatial features in scaled PL maps.