Exciton Cooling in 2D Perovskite Nanoplatelets: Rationalized Carrier-Induced Stark and Phonon Bottleneck Effects,The Journal of Physical Chemistry Letters

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Exciton Cooling in 2D Perovskite Nanoplatelets: Rationalized Carrier-Induced Stark and Phonon Bottleneck Effects
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2022-01-05 , DOI: 10.1021/acs.jpclett.1c03894
Carolina Villamil Franco ₁ , Gaëlle Trippé-Allard ₂ , Benoît Mahler ₃ , Christian Cornaggia ₁ , Jean-Sébastien Lauret ₂ , Thomas Gustavsson ₁ , Elsa Cassette _{1,

2}

Affiliation

Using femtosecond transient absorption (fs-TA), we investigate the hot exciton relaxation dynamics in strongly confined lead iodide perovskite nanoplatelets (NPLs). The large quantum and dielectric confinement leads to discrete excitonic transitions and strong Stark features in the TA spectra. This prevents the use of conventional relaxation analysis methods extracting the carrier temperature or measuring the buildup of the band-edge bleaching. Instead, we show that the TA spectral line shape near the band-edge reflects the state of the system, which can be used to probe the exciton cooling dynamics. The ultrafast hot exciton relaxation in one- to three- monolayer-thick NPLs confirms the absence of intrinsic phonon bottleneck. However, excitation fluence-dependent measurements reveal a hot phonon bottleneck effect, which is found to be independent of the nature of the internal cations but strongly affected by the ligands and/or sample surface state. Together, these results suggest a role of the surface ligands in the cooling process.

中文翻译：

二维钙钛矿纳米片中的激子冷却：合理的载流子诱导的斯塔克和声子瓶颈效应

使用飞秒瞬态吸收 (fs-TA)，我们研究了强约束碘化铅钙钛矿纳米片 (NPL) 中的热激子弛豫动力学。大的量子和介电限制导致 TA 光谱中的离散激子跃迁和强烈的斯塔克特征。这可以防止使用传统的弛豫分析方法来提取载体温度或测量带边漂白的累积。相反，我们表明带边缘附近的 TA 谱线形状反映了系统的状态，可用于探测激子冷却动力学。一到三层厚的 NPL 中的超快热激子弛豫证实了不存在固有的声子瓶颈。然而，依赖于激发能量密度的测量揭示了热声子瓶颈效应，发现它与内部阳离子的性质无关，但受配体和/或样品表面状态的强烈影响。总之，这些结果表明表面配体在冷却过程中的作用。

更新日期：2022-01-13

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