Femtosecond Time-Resolved Transient Absorption Spectroscopy of CH3NH3PbI3 Perovskite Films: Evidence for Passivation Effect of PbI2

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• 作者：Lili Wang ; Christopher McCleese ; Anton Kovalsky ; Yixin Zhao ; Clemens Burda
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：September 3, 2014
• 年：2014
• 卷：136
• 期：35
• 页码：12205-12208
• 全文大小：290K
• ISSN：1520-5126

文摘

CH₃NH₃PbI₃ perovskite layered films deposited on substrates with and without a titania support structure have been prepared and studied using time-resolved femtosecond transient absorption (fs-TA) spectroscopy in the visible light range (450鈥?00 nm). The electron injection dynamics from the photoexcited perovskite layers to the neighboring film structures could be directly monitored via the transient bleaching dynamics of the perovskite at 鈭?50 nm and thus systematically studied as a function of the layer-by-layer architecture. In addition, for the first time we could spectrally distinguish transient bleaching at 鈭?50 nm from laser-induced fluorescence that occurs red-shifted at 鈭?80 nm. We show that an additional bleach feature at 鈭?10 nm appears when PbI₂ is present in the perovskite film. The amplitudes of the PbI₂ and perovskite TA peaks were compared to estimate relative amounts of PbI₂ in the samples. Kinetic analysis reveals that perovskite films with less PbI₂ show faster relaxation rates than those containing more PbI₂. These fast dynamics are attributed to charge carrier trapping at perovskite grain boundaries, and the slower dynamics in samples containing PbI₂ are due to a passivation effect, in line with other recently reported work.