Unveiling the Electronic Band Structure and Temporal Dynamics of Excited Carriers in Formamidinium Lead Bromide Perovskite,Advanced Optical Materials

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Unveiling the Electronic Band Structure and Temporal Dynamics of Excited Carriers in Formamidinium Lead Bromide Perovskite
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2024-01-15 , DOI: 10.1002/adom.202302013
Giuseppe Ammirati _{1,

2} , Stefano Turchini ₁ , Francesco Toschi ₁ , Patrick O'Keeffe ₃ , Alessandra Paladini ₃ , Faustino Martelli ₄ , Fabio Matteocci ₂ , Jessica Barichello ₂ , Paolo Moras ₅ , Polina M. Sheverdyaeva ₅ , Valeria Milotti ₅ , Daniel Ory _{6,

7} , Aldo Di Carlo _{1,

2} , Daniele Catone ₁

Affiliation

In this study, the electronic band structure and the dynamics of the excited carriers in the formamidinium lead bromide (FAPbBr₃) perovskite are investigated by combining the information obtained from steady-state absorption, photoluminescence, femtosecond transient absorption spectroscopy, photoelectron spectroscopy, and density functional theory calculations. A detailed description of the electronic transitions in the UV–vis energy range has been provided, giving an estimation of the exciton binding energy (40 ± 5 meV), the transition energy from the first valence band (VB1) to the conduction band (CB1) (electronic bandgap at 2.37 ± 0.01 eV) and assigning the broad peak at ≈3.4 eV to the transition from the second innermost valence band (VB2) to CB1. The temporal dynamics of the excited carriers involved in these transitions are investigated using different excitation energies and carrier densities. Different trends are observed in the dynamics of the transient signals associated with the VB1→CB1 (PB1) and VB2→CB1 (PB2) transitions. As the carrier density increased, PB1 exhibited a slowing down of its rise time, while PB2 showed an acceleration attributed to the thermalization of the excited holes in VB2. These valuable findings have the potential to unlock new strategies aimed at maximizing the efficiencies and performance of perovskite-based solar cell devices.

中文翻译：

揭示甲脒溴化铅钙钛矿中激发载流子的电子能带结构和时间动力学

在本研究中，通过结合从稳态吸收、光致发光、飞秒瞬态吸收光谱、光电子能谱和密度获得的信息，研究了甲脒溴化铅（FAPbBr ₃）钙钛矿中的电子能带结构和激发载流子的动力学。泛函理论计算。提供了 UV-vis 能量范围内电子跃迁的详细描述，给出了激子结合能 (40 ± 5 meV)、从第一价带 (VB1) 到导带 (CB1) 的跃迁能量的估计）（电子带隙为 2.37 ± 0.01 eV），并将约 3.4 eV 处的宽峰指定为从第二个最内层价带 (VB2) 到 CB1 的跃迁。使用不同的激发能量和载流子密度研究了这些跃迁中涉及的受激载流子的时间动力学。在与 VB1→CB1 (PB1) 和 VB2→CB1 (PB2) 转换相关的瞬态信号动态中观察到不同的趋势。随着载流子密度的增加，PB1 的上升时间减慢，而 PB2 则由于 VB2 中激发空穴的热化而加速。这些有价值的发现有可能开启新策略，旨在最大限度地提高基于钙钛矿的太阳能电池器件的效率和性能。

更新日期：2024-01-15

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