理论计算研究半导体晶体表面能与能带各向异性对光生电荷分离的影响

A theoretical investigation on the effects of surface energy and band energy anisotropy of semiconductor crystals on photogenerated charge separation

利用半导体晶面工程促进电荷分离是提高光催化反应效率的重要措施之一,但如何理解和解释其分离机制还存在诸多争议.针对3个典型的半导体体系TiO2(锐钛矿)、Cu2WS4和SrTiO3,利用密度泛函理论计算,从表面能和体相能带的各向异性这两个角度来探讨它们对光生电子-空穴对分离的影响.结果表明,晶面表面能的差异是发生电荷分离的必要条件,而利用体相能带的各向异性能够解释实验中观测到的电荷分离方向.

Using crystal facet engineering of semiconductors to generate the photogenerated charge separation is an important measure to improve the efficiency of photocatalytic reaction.However,there are still many controversies over how to understand and explain the separation mechanism.In this paper,three typical semiconductor systems,TiO2(anatase),Cu2WS4 and SrTiO3,are studied using density functional theory,and the effects of surface energy and band energy anisotropy on photogenerated electron-hole pair separation are explored.The results indicate that the difference in surface energy is the necessary condition for charge separation.Moreover,band energy anisotropy along different facet directions is an important intrinsic factor for charge separation.