Probing Lattice Dynamics in Two-Dimensional Inorganic Pseudohalide Perovskites with Ultrafast Infrared Spectroscopy
Probing Lattice Dynamics in Two-Dimensional Inorganic Pseudohalide Perovskites with Ultrafast Infrared Spectroscopy
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DOI：
10.1021/acs.jpcc.2c03516
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发表时间：
2022-06
期刊：
影响因子：
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通讯作者：
Xiangyu Xing;Jiayi Li;J. Breen;J. Nishida;H. Karunadasa;M. Fayer
中科院分区：
文献类型：
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作者：
Xiangyu Xing;Jiayi Li;J. Breen;J. Nishida;H. Karunadasa;M. Fayer
二维(2D)卤化物钙钛矿中的动态晶格无序可以通过载流子/激子−晶格相互作用对其光学性质产生重要影响。此前，2D卤化物−类卤化物钙钛矿(MA)2Pb(SCN)2I2(MA+=甲铵)具有动态非均匀晶格，结构演化发生在皮秒时间尺度上。在这里，我们研究了两个纯无机的2D钙钛矿，Cs2Ph(SCN)2X2(X=Br或I)。利用二维红外光谱(2D IR)和偏振选择泵浦−探针(PSPP)实验研究了卤化物阴离子变化的动力学和ff效应。振动探头采用12cN伸缩模式。fiLMS是同位素掺杂的，∼99%13CN，以避免过度的红外吸收、加热和振动激发转移。为了提高信噪比，在薄的fiLMS上使用反射几何结构进行了PSPP测量。结果表明，Cs2Ph(SCN)2X2中的12CN振动寿命明显高于(MA)2Ph(SCN)2I2中的12CN振动寿命，而Br型和I型Cs2Pb2X2的fi寿命基本相同。用二维红外光谱测量了非均匀展宽的CN拉伸吸收谱线的光谱扩散(结构演化)和均匀退相。与(MA)2Pb(SCN)2I2相比，Cs2Pb(SCN)2×22D钙钛矿的结构演化明显缓慢。光谱扩散不受卤化物阴离子的影响。此外，由于CN伸展与晶格声子的耦合，还存在明显的fi不均匀退相现象。我们的fi结果提供了对无机2D钙钛矿晶格动力学的深入了解，并为研究其复杂的载流子/激子−晶格相互作用奠定了基础，这对于在光电子器件中的应用具有重要意义。
: Dynamic lattice disorder in two-dimensional (2D) halide perovskites can play an important role in their optical properties through carrier/exciton − lattice interactions. Previously, the 2D halide − pseudohalide perovskite (MA) 2 Pb(SCN) 2 I 2 (MA + = methylammonium) was demonstrated to have a dynamically inhomogeneous lattice with structural evolution occurring on a picosecond time scale. Here, we have investigated two purely inorganic 2D perovskites, Cs 2 Pb(SCN) 2 X 2 (X = Br or I). 2D infrared (2D IR) and polarization-selective pump − probe (PSPP) experiments were used to study dynamics and the e ff ects of changing the halide anions. The 12 CN stretching mode was used as the vibrational probe. The fi lms were isotopically doped, ∼ 99% 13 CN, to avoid excessive IR absorption, heating, and vibrational excitation transfer. PSPP measurements were performed on thin fi lms using the re fl ection geometry to improve the signal-to-noise ratio. The results showed that the 12 CN vibrational lifetime in Cs 2 Pb(SCN) 2 X 2 is signi fi cantly longer than that in (MA) 2 Pb(SCN) 2 I 2 , and the lifetimes were essentially the same for Br and I analogues of Cs 2 Pb(SCN) 2 X 2 . 2D IR spectroscopy is carried out to measure both spectral di ff usion (structural evolution) and homogeneous dephasing of the inhomogeneously broadened CN stretch absorption line. The Cs 2 Pb(SCN) 2 X 2 2D perovskites displayed substantially slower structural evolution compared to (MA) 2 Pb(SCN) 2 I 2 . The spectral di ff usion is independent of the halide anion. There is also signi fi cant homogeneous dephasing caused by the coupling of the CN stretch to lattice phonons. Our fi ndings provide insights into lattice dynamics of inorganic 2D perovskites and lay a foundation for studies on their complex carrier/exciton − lattice interactions, of importance for applications in optoelectronic devices.