School of Electronic Science and Engineering (National Model Microelectronics College), Xiamen University, Xiamen 361005, People's Republic of China.
Nanoscale. 2019 Nov 21;11(45):21867-21871. doi: 10.1039/c9nr06834a.
Two-dimensional (2D) Ruddlesden-Popper perovskites with bulky organic cations have attracted extensive attention in light-emitting devices and photovoltaics due to their robust environment stability, tunable luminescent color, strong exciton binding and promising efficiency. A quantum well (QW) structure is spontaneously formed by sandwiching PbBr4 layers into bulky organic cations. However, some intrinsic excitonic mechanisms in these materials still need to be elucidated. In this study, the exciton-phonon interaction of quasi-2D (PEA)2(CsPbBr3)n-1PbBr4 with different PbBr4 layer numbers (n) was analyzed by temperature-varied photoluminescence (PL), scanning electron microscopy (SEM) and powder X-ray diffraction (PXRD). The mechanism of bandgap shifting with temperature was found to be dominated by the thermal expansion effect in the large-n 2D and bulk perovskite, and gradually switched to exciton-phonon interaction in the n = 1 (PEA)2PbBr4 phase, indicating enhanced exciton-phonon interaction in the thinner quantum well structure. Further analysis showed that the enhanced exciton-phonon interaction originated from the longitudinal optical phonon-exciton Fröhlich interaction rather than acoustic phonon-exciton coupling. We believe that our results will benefit the further optimization of light-emitting devices based on 2D perovskites.
二维（2D）Ruddlesden-Popper 型钙钛矿具有较大的有机阳离子，由于其环境稳定性强、发光颜色可调、激子结合强和效率高，在发光器件和光伏领域引起了广泛关注。PbBr4 层夹在大体积有机阳离子中，自发形成量子阱（QW）结构。然而，这些材料中的一些内在激子机制仍需要阐明。在这项研究中，通过变温光致发光（PL）、扫描电子显微镜（SEM）和粉末 X 射线衍射（PXRD）分析了不同 PbBr4 层数（n）的准二维（PEA）2（CsPbBr3）n-1PbBr4 的激子-声子相互作用。发现随着温度的能带隙移动机制主要由大 n 二维和体相钙钛矿的热膨胀效应主导，而在 n = 1（PEA）2PbBr4 相中逐渐转变为激子-声子相互作用，表明在较薄的量子阱结构中激子-声子相互作用增强。进一步分析表明，增强的激子-声子相互作用源于纵光学声子-激子 Frohlich 相互作用，而不是声子-激子耦合。我们相信，我们的研究结果将有助于进一步优化基于二维钙钛矿的发光器件。
