Wei Yaqing, Long Run
College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education , Beijing Normal University , Beijing 100875 , P. R. China.
J Phys Chem Lett. 2018 Jul 19;9(14):3856-3862. doi: 10.1021/acs.jpclett.8b01654. Epub 2018 Jun 29.
Using time-domain density functional theory combined with nonadiabatic molecular dynamics, we demonstrate that both symmetrical (GB_s) and asymmetrical grain boundaries (GB_a) significantly extend charge-carrier lifetime compared with monolayer black phosphorus. Boundaries create no deep trap states, which decrease electron-phonon coupling. As a result, GB_s increases carrier lifetime by a factor of 22, whereas GB_a extends the lifetime by a factor of 4. More importantly, the interplay between the immobile electron localized at the boundaries in the GB_s and extended excited-state lifetime facilitates a chemical reaction, which is beneficial for photocatalysts. In contrast, GB_a separates electron and hole spatially in different locations, which forms a long-lived charge-separated state and is favorable for photovoltaics. Our simulations demonstrate that grain boundaries are benign and retard nonradiative electron-hole recombination in monolayer black phosphorus, suggesting a route to reduce energy losses via rational choice of defect to realize high-performance photovoltaic and photocatalytic devices.
利用时域密度泛函理论结合非绝热分子动力学，我们证明，与单层黑磷相比，对称（GB_s）和非对称晶界（GB_a）均显著延长了电荷载流子寿命。晶界不会产生深陷阱态，从而降低了电子-声子耦合。结果，GB_s使载流子寿命增加了22倍，而GB_a使寿命延长了4倍。更重要的是，GB_s中固定在晶界处的电子与延长的激发态寿命之间的相互作用促进了化学反应，这对光催化剂有利。相比之下，GB_a在空间上将电子和空穴分隔在不同位置，形成了长寿命电荷分离态，有利于光伏应用。我们的模拟表明，晶界是良性的，可抑制单层黑磷中的非辐射电子-空穴复合，这为通过合理选择缺陷来减少能量损失以实现高性能光伏和光催化器件提供了一条途径。
