Zhong Chengmei, Sangwan Vinod K, Kang Joohoon, Luxa Jan, Sofer Zdeněk, Hersam Mark C, Weiss Emily A
Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , United States.
Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States.
J Phys Chem Lett. 2019 Feb 7;10(3):493-499. doi: 10.1021/acs.jpclett.8b03543. Epub 2019 Jan 17.
Layered indium selenide (InSe) is a van der Waals solid that has emerged as a promising material for high-performance ultrathin solar cells. The optoelectronic parameters that are critical to photoconversion efficiencies, such as hot carrier lifetime and surface recombination velocity, are however largely unexplored in InSe. Here, these key photophysical properties of layered InSe are measured with femtosecond transient reflection spectroscopy. The hot carrier cooling process is found to occur through phonon scattering. The surface recombination velocity and ambipolar diffusion coefficient are extracted from fits to the pump energy-dependent transient reflection kinetics using a free carrier diffusion model. The extracted surface recombination velocity is approximately an order of magnitude larger than that for methylammonium lead-iodide perovskites, suggesting that surface recombination is a principal source of photocarrier loss in InSe. The extracted ambipolar diffusion coefficient is consistent with previously reported values of InSe carrier mobility.
层状硒化铟（InSe）是一种范德华固体，已成为用于高性能超薄太阳能电池的有前景的材料。然而，对于光转换效率至关重要的光电参数，如热载流子寿命和表面复合速度，在InSe中很大程度上尚未得到研究。在此，利用飞秒瞬态反射光谱法测量了层状InSe的这些关键光物理性质。发现热载流子冷却过程是通过声子散射发生的。使用自由载流子扩散模型，从对泵浦能量依赖的瞬态反射动力学的拟合中提取表面复合速度和双极性扩散系数。提取的表面复合速度比甲基铵铅碘钙钛矿的表面复合速度大约一个数量级，这表明表面复合是InSe中光载流子损失的主要来源。提取的双极性扩散系数与先前报道的InSe载流子迁移率值一致。
