Fate of Optical Excitons in FAPbI3 Nanocube Superlattices,ACS Photonics

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Fate of Optical Excitons in FAPbI3 Nanocube Superlattices
ACS Photonics ( IF 6.5 ) Pub Date : 2024-09-04 , DOI: 10.1021/acsphotonics.4c00105
Alessandra Milloch _{1,

2,

3} , Umberto Filippi ₄ , Paolo Franceschini _{5,

6} , Selene Mor _{1,

2} , Stefania Pagliara _{1,

2} , Gabriele Ferrini _{1,

2} , Franco V. A. Camargo ₇ , Giulio Cerullo _{7,

8} , Dmitry Baranov _{4,

9} , Liberato Manna ₄ , Claudio Giannetti _{1,

2,

5}

Affiliation

Understanding the nature of the photoexcitation and ultrafast charge dynamics pathways in organic halide perovskite nanocubes and their aggregation into superlattices is key for potential applications as tunable light emitters, photon-harvesting materials, and light-amplification systems. In this work, we apply two-dimensional coherent electronic spectroscopy (2DES) to track in real time the formation of near-infrared optical excitons and their ultrafast relaxation in CH(NH₂)₂PbI₃ nanocube superlattices. Our results unveil that the coherent ultrafast dynamics is limited by the combination of the inherent short exciton decay time (≃40 fs) and the dephasing due to the coupling with selective optical phonon modes at higher temperatures. On the picosecond time scale, we observe the progressive formation of long-lived localized trap states. The analysis of the temperature dependence of the excitonic intrinsic line width, as extracted by the antidiagonal components of the 2D spectra, unveils a dramatic change of the excitonic coherence time across the cubic to tetragonal structural transition. Our results offer a new way to control and enhance the ultrafast coherent dynamics of photocarrier generation in hybrid halide perovskite synthetic solids.

中文翻译：

FAPbI3 纳米立方体超晶格中光学激子的命运

了解有机卤化物钙钛矿纳米立方体中的光激发和超快电荷动力学路径的性质及其聚集成超晶格是可调谐光发射器、光子捕获材料和光放大系统等潜在应用的关键。在这项工作中，我们应用二维相干电子光谱（2DES）实时跟踪CH(NH ₂ ) ₂ PbI ₃纳米立方体超晶格中近红外光学激子的形成及其超快弛豫。我们的结果表明，相干超快动力学受到固有的短激子衰减时间（≃40 fs）和由于在较高温度下与选择性光学声子模式耦合导致的移相相结合的限制。在皮秒时间尺度上，我们观察到长期局部陷阱态的逐渐形成。通过二维光谱的反对角分量提取的激子本征线宽的温度依赖性分析揭示了激子相干时间在立方结构到四方结构转变过程中的巨大变化。我们的研究结果提供了一种控制和增强混合卤化物钙钛矿合成固体中光载流子生成的超快相干动力学的新方法。

更新日期：2024-09-04

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