Hot Phonon Bottleneck Stimulates Giant Optical Gain in Lead Halide Perovskite Quantum Dots,ACS Photonics

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Hot Phonon Bottleneck Stimulates Giant Optical Gain in Lead Halide Perovskite Quantum Dots
ACS Photonics ( IF 6.5 ) Pub Date : 2022-09-29 , DOI: 10.1021/acsphotonics.2c01394
Zhonghui Nie ₁ , Zhigao Huang ₁ , Mingshui Zhang ₁ , Baoqiang Wu ₁ , Haoyu Wu ₂ , Yongliang Shi ₂ , Kaifeng Wu ₃ , Yue Wang ₁

Affiliation

Hot phonon bottleneck (HPB), one of the dominant effects for tuning hot carrier (HC) cooling, has been extensively studied in lead halide perovskites (LHP), and most attention has been devoted to its role in those photovoltaic devices. However, behaviors of HPB in strongly confined systems and its influence on optical gain remain obscure. Herein, by monitoring state-resolved relaxation in strongly confined CsPbBr₃ quantum dots (QDs), we discover a discrete cooling process of HCs and demonstrate that their elongation, induced by HPB, primarily occurs during the intraband relaxation from the first excited (1P) to the lowest (1S) states. Moreover, a threshold-like character of HPB in LHP QDs, where the energy dissipation rate significantly drops only beyond a certain carrier density, could be ascribed to the nonadiabatic interaction by coupling with ligand vibrations. Remarkably, HPB has been found to trigger the formation of a giant optical gain (6000 cm^–1) near the second absorption peak, and spectral analysis indicates its origin from population inversion at the higher-transition or 1P state. Our findings could strengthen the understanding of photophysics in LHP QDs and guide the development of efficient and broadband lighting applications.

中文翻译：

热声子瓶颈刺激卤化铅钙钛矿量子点中的巨大光学增益

热声子瓶颈 (HPB) 是调节热载流子 (HC) 冷却的主要效应之一，已在卤化铅钙钛矿 (LHP) 中得到广泛研究，并且大部分注意力都集中在其在这些光伏器件中的作用。然而，HPB 在强受限系统中的行为及其对光学增益的影响仍然不清楚。在此，通过监测强约束 CsPbBr ₃量子点 (QD) 中的状态分辨弛豫，我们发现了一个离散的HCs 的冷却过程，并证明由 HPB 引起的它们的伸长主要发生在从第一个激发态 (1P) 到最低 (1S) 态的带内弛豫过程中。此外，LHP QDs 中 HPB 的阈值特征，其中能量耗散率仅在一定载流子密度之外显着下降，可归因于通过与配体振动耦合的非绝热相互作用。值得注意的是，已发现 HPB 会在第二个吸收峰附近触发巨大的光学增益 (6000 cm ^-1 ) 的形成，光谱分析表明其起源于较高跃迁或 1P 状态下的布居反转。我们的研究结果可以加强对 LHP QD 中光物理学的理解，并指导高效和宽带照明应用的开发。

更新日期：2022-09-29

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