Wei Yaqing, Zhou Zhaohui, Long Run
College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University , Beijing 100875, People's Republic of China.
International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University , Xi'an 710049, People's Republic of China.
J Phys Chem Lett. 2017 Sep 21;8(18):4522-4529. doi: 10.1021/acs.jpclett.7b02099. Epub 2017 Sep 8.
Layered TiS materials hold appealing potential in photovoltaics and optoelectronics due to their excellent electronic and optical properties. Using time domain density functional theory combined with nonadiabatic (NA) molecular dynamics, we show that the electron-hole recombination in pristine TiS nanoribbons (NRs) occurs in tens of picoseconds and is over 10-fold faster than the experimental value. By performing an atomistic ab initio simulation with a sulfur vacancy, we demonstrate that a sulfur vacancy greatly reduces electron-hole recombination, achieving good agreement with experiment. Introduction of a sulfur vacancy increases the band gap slightly because the NR's highest occupied molecular orbital is lowered in energy. More importantly, the sulfur vacancy partially diminishes the electron and hole wave functions' overlap and reduces NA electron-phonon coupling, which competes successfully with the longer decoherence time, slowing down recombination. Our study suggests that a rational choice of defects can control nonradiative electron-hole recombination in TiS NRs and provides mechanistic principles for photovoltaic and optoelectronic device design.
层状硫化钛材料因其优异的电子和光学特性，在光伏和光电子领域具有诱人的潜力。通过结合时域密度泛函理论与非绝热（NA）分子动力学，我们发现原始硫化钛纳米带（NRs）中的电子 - 空穴复合发生在几十皮秒内，比实验值快10倍以上。通过对硫空位进行原子从头算模拟，我们证明硫空位极大地减少了电子 - 空穴复合，与实验结果吻合良好。引入硫空位会使带隙略有增加，因为纳米带的最高占据分子轨道能量降低。更重要的是，硫空位部分减小了电子和空穴波函数的重叠，并降低了非绝热电子 - 声子耦合，成功地与更长的退相干时间竞争，减缓了复合过程。我们的研究表明，合理选择缺陷可以控制硫化钛纳米带中的非辐射电子 - 空穴复合，并为光伏和光电器件设计提供机理原理。
