Ma Jie, Gao Shiwu
Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics and Advanced Research Institute of Multidisciplinary Science , Beijing Institute of Technology , Beijing 100081 , China.
Beijing Computational Science Research Center , Beijing 100193 , China.
ACS Nano. 2019 Dec 24;13(12):13658-13667. doi: 10.1021/acsnano.9b03555. Epub 2019 Aug 12.
Plasmon-induced electron-hole separation at metal-semiconductor interfaces is an essential step in photovoltaics, photochemistry, and optoelectronics. Despite its importance in fundamental understandings and technological applications, the mechanism and dynamics of the charge separation under plasmon excitations have not been well understood. Here, the plasmon-induced charge separation between a Ag nanocluster and a TiO(110) surface is investigated using time-dependent density functional theory simulations. It is found that the charge separation dynamics consists of two processes: during the first 10 fs an initial charge separation resulting from the plasmon-electron coupling at the interface and a subsequent charge redistribution governed by the sloshing motion of the charge-transfer plasmon. The interplay between the two processes determines the charge separation and leads to the inhomogeneous layer-dependent distribution of hot carriers. The hot electrons are more efficient than the hot holes in the charge injection, resulting in the charge separation. Over 40% of the hot electron-hole pairs are separated spatially from the interface. Finally, the second TiO layer receives the most net charges from the Ag nanocluster rather than the interfacial layer. These results reveal the mechanism and dynamics of the charge separation driven by the surface plasmon excitation and have broad implications in plasmonic applications.
金属 - 半导体界面处的等离子体激元诱导的电子 - 空穴分离是光伏、光化学和光电子学中的关键步骤。尽管其在基础理解和技术应用方面具有重要性，但等离子体激元激发下电荷分离的机制和动力学尚未得到充分理解。在此，使用含时密度泛函理论模拟研究了银纳米团簇与TiO(110)表面之间的等离子体激元诱导的电荷分离。研究发现，电荷分离动力学由两个过程组成：在前10飞秒内，界面处的等离子体激元 - 电子耦合导致初始电荷分离，随后电荷转移等离子体的晃动运动主导电荷重新分布。这两个过程之间的相互作用决定了电荷分离，并导致热载流子的层依赖不均匀分布。热电子在电荷注入方面比热空穴更有效，从而导致电荷分离。超过40%的热电子 - 空穴对在空间上与界面分离。最后，第二层TiO从银纳米团簇接收的净电荷最多，而不是界面层。这些结果揭示了表面等离子体激元激发驱动的电荷分离机制和动力学，在等离子体应用中具有广泛的意义。
