Ultrafast transient infrared spectroscopy for probing trapping states in hybrid perovskite films.
Ultrafast transient infrared spectroscopy for probing trapping states in hybrid perovskite films.
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DOI：
10.1038/s42004-022-00683-7
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发表时间：
2022-05-30
影响因子：
5.9
通讯作者：
Mohammed, Omar F.
中科院分区：
文献类型：
--
作者：
El-Zohry, Ahmed M.;Turedi, Bekir;Alsalloum, Abdullah;Maity, Partha;Bakr, Osman M.;Ooi, Boon S.;Mohammed, Omar F.
研究钙钛矿材料的电荷动力学是了解这些材料在各个领域的优异性能的关键一步。在这里，我们利用中红外区的瞬时吸收，其中只有导带中的电子信号被监测，而没有来自其他动力学物种的外部贡献。在4000 nm到6000 nm(2500-1666 cm−1)的测量范围内，可以很容易地监测到激发载流子的复合和捕获过程。此外，我们还发现在这一光谱范围内，捕获过程可以与复合过程区分开来，在复合过程中，与溴基衍生物相比，碘化物膜更倾向于捕获激发电子。由于在中红外区域有发射，因此指定了俘获过程，而传统的带隙复合过程不存在这一过程。测试了薄膜成分、激发依赖关系和探测波长等参数。本研究为钙钛矿薄膜的中红外吸收开辟了新的前沿，定性和定量地研究了钙钛矿膜的捕获过程，以及钙钛矿薄膜在中红外区域的潜在应用。卤化物基钙钛矿薄膜是太阳能电池中常用的吸收材料，但电荷复合和陷阱等不良影响继续限制着创纪录的转换效率。在这里，作者使用飞秒瞬变中红外光谱来阐明不同组成的钙钛矿薄膜的导带中的电子复合和陷阱。
Studying the charge dynamics of perovskite materials is a crucial step to understand the outstanding performance of these materials in various fields. Herein, we utilize transient absorption in the mid-infrared region, where solely electron signatures in the conduction bands are monitored without external contributions from other dynamical species. Within the measured range of 4000 nm to 6000 nm (2500–1666 cm−1), the recombination and the trapping processes of the excited carriers could be easily monitored. Moreover, we reveal that within this spectral region the trapping process could be distinguished from recombination process, in which the iodide-based films show more tendencies to trap the excited electrons in comparison to the bromide-based derivatives. The trapping process was assigned due to the emission released in the mid-infrared region, while the traditional band-gap recombination process did not show such process. Various parameters have been tested such as film composition, excitation dependence and the probing wavelength. This study opens new frontiers for the transient mid-infrared absorption to assign the trapping process in perovskite films both qualitatively and quantitatively, along with the potential applications of perovskite films in the mid-IR region. Halide-based perovskite films are popular absorber materials used in solar cells, but undesired effects such as charge recombination and trapping continue to cap record conversion efficiencies. Here, the authors use femtosecond transient mid-infrared spectroscopy to elucidate electron recombination and trapping in the conduction bands of various compositions of perovskite thin films.
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