Free Carriers versus Excitons in CH3NH3PbI3 Perovskite Thin Films at Low Temperatures: Charge Transfer from the Orthorhombic Phase to the Tetragonal Phase

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• 作者：Le Quang Phuong ; Yasuhiro Yamada ; Masaya Nagai ; Naoki Maruyama ; Atsushi Wakamiya ; Yoshihiko Kanemitsu
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2016
• 出版时间：July 7, 2016
• 年：2016
• 卷：7
• 期：13
• 页码：2316-2321
• 全文大小：420K
• 年卷期：0
• ISSN：1948-7185

文摘

We have investigated the dynamic optical properties of CH₃NH₃PbI₃ (MAPbI₃) perovskite thin films at low temperatures using time-resolved photoluminescence, optical transient absorption (TA), and THz TA spectroscopy. Optical spectroscopic results indicate that the high-temperature tetragonal phase still remains in the MAPbI₃ thin films at low temperatures in addition to the major orthorhombic phase. The fast charge transfer from the orthorhombic phase to the tetragonal phase is likely to suppress the formation of excitons in the orthorhombic phase. Consequently, the near-band-edge optical responses of the photocarriers in both the tetragonal and orthorhombic phases of the MAPbI₃ thin films are more accurately described by a free-carrier model, rather than an excitonic model even at low temperatures.