Chu Weibin, Saidi Wissam A, Zheng Qijing, Xie Yu, Lan Zhenggang, Prezhdo Oleg V, Petek Hrvoje, Zhao Jin
Department of Mechanical Engineering and Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao, Shandong 266101, China.
J Am Chem Soc. 2016 Oct 19;138(41):13740-13749. doi: 10.1021/jacs.6b08725. Epub 2016 Oct 5.
Photogenerated charge carrier dynamics near molecule/TiO interfaces are important for the photocatalytic and photovoltaic processes. To understand this fundamental aspect, we performed a time-domain ab initio nonadiabatic molecular dynamics study of the photogenerated hole dynamics at the CHOH/rutile TiO(110) interface. We studied the forward and reverse hole transfer between TiO and CHOH as well as the hole energy relaxation to the valence band maximum. First, we show that the hole-trapping ability of CHOH depends strongly on the adsorption structure. Only when the CHOH is deprotonated to form chemisorbed CHO will ∼15% of the hole be trapped by the molecule. Second, we find that strong fluctuations of the HOMO energies of the adsorbed molecules induced by electron-phonon coupling provide additional channels, which accelerate the hole energy relaxation. Third, we demonstrate that the charge transfer and energy relaxation processes depend significantly on temperature. When the temperature decreases from 100 to 30 K, the forward hole transfer and energy relaxation processes are strongly suppressed because of the reduction of phonon occupation. These results indicate that the molecule/TiO energy level alignment, thermal excitation of a phonon, and electron-phonon coupling are the key factors that determine the photogenerated hole dynamics. Our studies provide valuable insights into the photogenerated charge and energy transfer dynamics at molecule/semiconductor interfaces.
分子/TiO界面附近的光生载流子动力学对于光催化和光伏过程至关重要。为了理解这一基本方面，我们对CHOH/金红石型TiO(110)界面处的光生空穴动力学进行了时域从头算非绝热分子动力学研究。我们研究了TiO和CHOH之间的正向和反向空穴转移以及空穴向价带最大值的能量弛豫。首先，我们表明CHOH的空穴捕获能力强烈依赖于吸附结构。只有当CHOH去质子化形成化学吸附的CHO时，约15%的空穴才会被分子捕获。其次，我们发现电子-声子耦合引起的吸附分子HOMO能量的强烈波动提供了额外的通道，加速了空穴能量弛豫。第三，我们证明电荷转移和能量弛豫过程显著依赖于温度。当温度从100 K降至30 K时，由于声子占据数的减少，正向空穴转移和能量弛豫过程受到强烈抑制。这些结果表明，分子/TiO能级排列、声子的热激发以及电子-声子耦合是决定光生空穴动力学的关键因素。我们的研究为分子/半导体界面处的光生电荷和能量转移动力学提供了有价值的见解。
