Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States.
J Phys Chem Lett. 2023 Mar 2;14(8):2106-2111. doi: 10.1021/acs.jpclett.2c03894. Epub 2023 Feb 20.
Transient extreme ultraviolet (XUV) spectroscopy is becoming a valuable tool for characterizing solar energy materials because it can separate photoexcited electron and hole dynamics with element specificity. Here, we use surface-sensitive femtosecond XUV reflection spectroscopy to separately measure photoexcited electron, hole, and band gap dynamics of ZnTe, a promising photocathode for CO reduction. We develop an ab initio theoretical framework based on density functional theory and the Bethe-Salpeter equation to robustly assign the complex transient XUV spectra to the material's electronic states. Applying this framework, we identify the relaxation pathways and quantify their time scales in photoexcited ZnTe, including subpicosecond hot electron and hole thermalization, surface carrier diffusion, ultrafast band gap renormalization, and evidence of acoustic phonon oscillations.
瞬态极紫外（XUV）光谱学正成为一种研究太阳能材料的重要工具，因为它可以通过元素特异性来分离光激发电子和空穴动力学。在这里，我们使用表面敏感的飞秒 XUV 反射光谱学来分别测量 ZnTe 的光激发电子、空穴和带隙动力学，ZnTe 是一种很有前途的 CO 还原光阴极。我们开发了一个基于密度泛函理论和 Bethe-Salpeter 方程的从头算理论框架，以将复杂的瞬态 XUV 光谱可靠地分配给材料的电子态。应用这个框架，我们确定了光激发 ZnTe 中的弛豫途径，并量化了它们的时间尺度，包括亚皮秒的热电子和空穴热化、表面载流子扩散、超快带隙重整化以及声子振动的证据。
