Exciton Formation Dynamics and Band-Like Free Charge-Carrier Transport in 2D Metal Halide Perovskite Semiconductors
Exciton Formation Dynamics and Band-Like Free Charge-Carrier Transport in 2D Metal Halide Perovskite Semiconductors
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DOI：
10.1002/adfm.202300363
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发表时间：
2023-05-01
影响因子：
19
通讯作者：
Herz, Laura M.
中科院分区：
文献类型：
--
作者：
Motti, Silvia G.;Kober-Czerny, Manuel;Herz, Laura M.
金属卤化物钙钛矿（MHP）半导体在过去十年中推动了光电技术的革命，特别是对于高效光伏应用。低维MHPs的电子约束在光发射和量子技术中有着广阔的应用前景。然而，这些应用的优化需要全面了解电荷载体的性质及其传输机制。本研究采用超快光学和太赫兹光谱相结合的研究声子能量，电荷载流子迁移率，和激子的形成在2D（PEA）（2）PbI 4和（BA）（2）PbI 4（其中PEA是苯乙胺和BA是丁基铵）。自由电荷载流子迁移率的温度依赖性测量揭示了这些强限制半导体中的带输运，具有令人惊讶的高面内迁移率。增强的电荷-声子耦合被示出为相对于（PEA）（2）PbI 4降低（BA）（2）PbI 4中的电荷载流子迁移率。激子和自由电荷载流子动力学解纠缠瞬态吸收和太赫兹光电导的同时监测。一个持续的自由电荷载流子人口观察，超过萨哈方程的预测，即使在低温下。这些研究结果提供了新的见解激子和自由载流子人口的温度依赖性的相互作用在2D MHP。此外，这种持续的自由电荷载流子数量和高迁移率证明了这些半导体用于诸如太阳能电池、晶体管和电驱动光源的应用的潜力。
Metal halide perovskite (MHP) semiconductors have driven a revolution in optoelectronic technologies over the last decade, in particular for high-efficiency photovoltaic applications. Low-dimensional MHPs presenting electronic confinement have promising additional prospects in light emission and quantum technologies. However, the optimisation of such applications requires a comprehensive understanding of the nature of charge carriers and their transport mechanisms. This study employs a combination of ultrafast optical and terahertz spectroscopy to investigate phonon energies, charge-carrier mobilities, and exciton formation in 2D (PEA)(2)PbI4 and (BA)(2)PbI4 (where PEA is phenylethylammonium and BA is butylammonium). Temperature-dependent measurements of free charge-carrier mobilities reveal band transport in these strongly confined semiconductors, with surprisingly high in-plane mobilities. Enhanced charge-phonon coupling is shown to reduce charge-carrier mobilities in (BA)(2)PbI4 with respect to (PEA)(2)PbI4. Exciton and free charge-carrier dynamics are disentangled by simultaneous monitoring of transient absorption and THz photoconductivity. A sustained free charge-carrier population is observed, surpassing the Saha equation predictions even at low temperature. These findings provide new insights into the temperature-dependent interplay of exciton and free-carrier populations in 2D MHPs. Furthermore, such sustained free charge-carrier population and high mobilities demonstrate the potential of these semiconductors for applications such as solar cells, transistors, and electrically driven light sources.