Two‐Photon Up‐Conversion Photoluminescence Realized through Spatially Extended Gap States in Quasi‐2D Perovskite Films
Two‐Photon Up‐Conversion Photoluminescence Realized through Spatially Extended Gap States in Quasi‐2D Perovskite Films
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DOI：
10.1002/adma.201901240
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发表时间：
2019-10
影响因子：
29.4
通讯作者：
Xixiang Zhu;Hengxing Xu;Yongtao Liu;Jia Zhang;Miaosheng Wang;I. Ivanov;O. Ovchinnikova;Bin Hu-Bin-H
中科院分区：
文献类型：
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作者：
Xixiang Zhu;Hengxing Xu;Yongtao Liu;Jia Zhang;Miaosheng Wang;I. Ivanov;O. Ovchinnikova;Bin Hu-Bin-H
报道了一种在溶液处理的准二维钙钛矿薄膜[（PEA）2（MA）4Pb 5 Br 16（n = 5）]中利用连续波（CW）红外光激发直接激发差距态产生双光子上转换光致发光（PL）的新方法.具体地，通过用CW 980 nm激光激发来激发差距态，观察到峰值在520 nm处的具有二次功率依赖性的可见光致发光，表明在准2D钙钛矿膜中发生双光子上转换光致发光。通过减小n值来减小差距状态导致双光子上转换PL信号的急剧减小。这证实了差距态确实负责在准2D钙钛矿中产生双光子上转换PL。此外，机械刮擦表明，不同n值的纳米片基本上均匀地形成在准2D钙钛矿膜中，以产生多光子上转换光发射。更重要的是，发现双光子上转换PL对外部磁场敏感，表明差距态基本上形成为准备多光子激发的空间扩展态。偏振相关的上转换PL研究表明，差距态通过库仑偏振经历轨道-轨道相互作用，形成空间扩展态，从而在准二维钙钛矿中发展多光子上转换发光。
A new approach to generate a two‐photon up‐conversion photoluminescence (PL) by directly exciting the gap states with continuous‐wave (CW) infrared photoexcitation in solution‐processing quasi‐2D perovskite films [(PEA)2(MA)4Pb5Br16 with n = 5] is reported. Specifically, a visible PL peaked at 520 nm is observed with the quadratic power dependence by exciting the gap states with CW 980 nm laser excitation, indicating a two‐photon up‐conversion PL occurring in quasi‐2D perovskite films. Decreasing the gap states by reducing the n value leads to a dramatic decrease in the two‐photon up‐conversion PL signal. This confirms that the gap states are indeed responsible for generating the two‐photon up‐conversion PL in quasi‐2D perovskites. Furthermore, mechanical scratching indicates that the different‐n‐value nanoplates are essentially uniformly formed in the quasi‐2D perovskite films toward generating multi‐photon up‐conversion light emission. More importantly, the two‐photon up‐conversion PL is found to be sensitive to an external magnetic field, indicating that the gap states are essentially formed as spatially extended states ready for multi‐photon excitation. Polarization‐dependent up‐conversion PL studies reveal that the gap states experience the orbit–orbit interaction through Coulomb polarization to form spatially extended states toward developing multi‐photon up‐conversion light emission in quasi‐2D perovskites.