Untangling free carrier and exciton dynamics in layered hybrid perovskites using ultrafast optical and terahertz spectroscopy
Untangling free carrier and exciton dynamics in layered hybrid perovskites using ultrafast optical and terahertz spectroscopy
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DOI：
10.1088/2053-1591/ad14c2
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发表时间：
2024-02-01
影响因子：
2.3
通讯作者：
Milot，Rebecca L.
中科院分区：
文献类型：
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作者：
Balogun，Folusho Helen;Gallop，Nathaniel P.;Milot，Rebecca L.
层状杂化钙钛矿(LPKs)由于其稳定性的提高，有望成为3D金属卤化物钙钛矿的替代品或添加剂，应用于光伏电池、LED和激光器等光电子学领域。然而，这些材料中高的激子结合能意味着在许多器件的工作条件下激子是主要物种。尽管掺入LPKs的器件的效率一直在提高，但这些材料中激子和自由电荷载流子之间的相互作用仍然是未知的，这是理解光电特性如何决定器件效率的关键信息。在本工作中，我们利用光泵/太赫兹探测光谱(OPTP)和可见光瞬时吸收光谱(TAS)分析了苯乙基碘化铅(PEA)_2PbI_4的光电性质和电荷-载流子动力学。我们在∼400fs的时间尺度上观察到了自由载流子的快速冷却和激子的形成，随后是速率常数为k2∼109 cm3 S−1的剩余自由电荷载流子较慢的双分子复合。激子复合通过两个单分子过程进行，寿命分别为t1∼11ps和t2∼83ps。此外，我们在瞬时吸收动力学轨迹中检测到激子-声子耦合的特征。这些发现为理解自由载流子和激子之间的相互作用提供了新的见解，并为进一步理解LPK中的电荷-载流子动力学提供了可能的机制。
Layered hybrid perovskites (LPKs) are promising as alternatives or additives to 3D metal halide perovskites for optoelectronic applications including photovoltaic cells, LEDs and lasers due to their increased stability. However, high exciton binding energies in these materials mean that excitons are the majority species under the operating conditions of many devices. Although the efficiency of devices that incorporate LPKs has been increasing, much is still unknown about the interplay of excitons and free charge-carriers in these materials, which is vital information for understanding how optoelectronic properties dictate device efficiency. In this work, we employ optical pump/THz probe spectroscopy (OPTP) and visible transient absorption spectroscopy (TAS) to analyse the optoelectronic properties and charge-carrier dynamics of phenylethylammonium lead iodide (PEA) 2 PbI 4. By combining these techniques, we are able to disentangle the contributions from excitons and free charge-carriers. We observe fast cooling of free charge-carriers and exciton formation on a timescale of∼ 400 fs followed by slower bimolecular recombination of residual free charge-carriers with a rate constant k 2∼ 10 9 cm 3 s− 1. Excitons recombine via two monomolecular processes with lifetimes t 1∼ 11 ps and t 2∼ 83 ps. Furthermore, we detect signatures of exciton–phonon coupling in the transient absorption kinetic traces. These findings provide new insight into the interplay between free charge-carriers and excitons as well as a possible mechanism to further understand the charge-carrier dynamics in LPKs.