Breaking Phonon Bottlenecks through Efficient Auger Processes in Perovskite Nanocrystals
Breaking Phonon Bottlenecks through Efficient Auger Processes in Perovskite Nanocrystals
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DOI：
10.1021/acsnano.2c12220
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发表时间：
2023-02-16
期刊：
影响因子：
17.1
通讯作者：
Kambhampati, Patanjali
中科院分区：
文献类型：
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作者：
Baker, Harry;Perez, Carlos Mora;Kambhampati, Patanjali
在钙钛矿中，热声子瓶颈一直受到密切的研究。对于钙钛矿纳米晶，可能存在热声子瓶颈和量子声子瓶颈。虽然人们普遍认为它们是存在的，但越来越多的证据表明，这两种形式的潜在声子瓶颈都已被打破。在这里，我们用态分辨泵浦/探测光谱(SRPP)和时间分辨光致发光光谱(t-PL)来揭示CsPbBr3和FAPbBr3块状15 nm纳米晶体模型体系的热激子弛豫动力学，其中FA为甲酰胺。SRPP数据可能被曲解为揭示了声子瓶颈，即使在低激子浓度下也是如此，那里应该没有激子浓度。我们用一种状态分辨的方法绕过了光谱问题，揭示了纳米晶体中可能预期的量子声子瓶颈的冷却和打破速度快了数量级。由于以前的泵浦/探测分析方法是模棱两可的，我们进行了t-PL实验来明确地证实热声子瓶颈的存在。T-PL实验表明，这些钙钛矿纳米晶中不存在热声子瓶颈。从头算分子动力学模拟通过包含有效的俄歇过程再现了实验。这项实验和理论工作揭示了热激子动力学的洞察力，如何精确测量它们，以及最终如何在这些材料中利用它们。
The hot phonon bottleneck has been under intense investigation in perovskites. In the case of perovskite nanocrystals, there may be hot phonon bottlenecks as well as quantum phonon bottlenecks. While they are widely assumed to exist, evidence is growing for the breaking of potential phonon bottlenecks of both forms. Here, we perform state-resolved pump/probe spectroscopy (SRPP) and time-resolved photoluminescence spectroscopy (t-PL) to unravel hot exciton relaxation dynamics in model systems of bulk-like 15 nm nanocrystals of CsPbBr3 and FAPbBr3 , with FA being formamidinium. The SRPP data can be misinterpreted to reveal a phonon bottleneck even at low exciton concentrations, where there should be none. We circumvent that spectroscopic problem with a state-resolved method that reveals an order of magnitude faster cooling and breaking of the quantum phonon bottleneck that might be expected in nanocrystals. Since the prior pump/probe methods of analysis are shown to be ambiguous, we perform t-PL experiments to unambiguously confirm the existence of hot phonon bottlenecks as well. The t-PL experiments reveal there is no hot phonon bottleneck in these perovskite nanocrystals. Ab initio molecular dynamics simulations reproduce experiments by inclusion of efficient Auger processes. This experimental and theoretical work reveals insight on hot exciton dynamics, how they are precisely measured, and ultimately how they may be exploited in these materials.