Using ultrafast broad-band transient absorption (TA) spectroscopy of photoexcited MAPbBr₃ thin films with probe continua in the visible and the mid- to deep-ultraviolet (UV) ranges, we capture the ultrafast renormalization at the fundamental gap at the R symmetry point of the Brillouin zone (BZ) and a higher energy gap at the M symmetry point. Advanced global lifetime analysis and lifetime density distribution analysis are applied to extract quantitative information. Our work confirms the similarity of the response at both high-symmetry points, which indicates a band edge renormalization that rises within the instrument response function (IRF, ∼250 fs) and decays in ca. 400–600 fs, undergoing an energy red shift of 90–150 meV. The reported time scale corresponds to the decay of free carriers into neutral excitons. The ability to monitor different high-symmetry points in photoexcited perovskites opens exciting prospects for the characterization of a large class of materials and for photonic applications.

中文翻译：

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钙钛矿中不同对称点的带隙重整化


使用光激发 MAPbBr ₃ 薄膜的超快宽带瞬态吸收 (TA) 光谱，并在可见光和中深紫外 (UV) 范围内进行连续探测，我们捕获了基频的超快重正化布里渊区 (BZ) 的 R 对称点处的能隙和 M 对称点处的更高能隙。应用先进的全局寿命分析和寿命密度分布分析来提取定量信息。我们的工作证实了两个高对称点处响应的相似性，这表明能带边缘重正化在仪器响应函数（IRF，~250 fs）内上升并在约 100 秒内衰减。 400–600 fs，经历 90–150 meV 的能量红移。报道的时间尺度对应于自由载流子衰变为中性激子。监测光激发钙钛矿中不同高对称点的能力为一大类材料的表征和光子应用开辟了令人兴奋的前景。