Importance of surface oxygen vacancies for ultrafast hot carrier relaxation and transport in Cu2O

Cu2O has appealing properties as an electrode for photo-electrochemical water splitting, yet its practical performance is severely limited by inefficient charge extraction at the interface. Using hybrid DFT calculations, we investigate carrier capture processes by oxygen vacancies (VO) in the experimentally observed (√3×√3)R30° reconstruction of the dominant (111) surface. Our results show that these VO are doubly ionized and that associated defects states strongly suppress electron transport. In particular, the excited electronic state of a singly charged VO plays a crucial role in the non-radiative electron capture process with a capture coefficient of about 10^-9 cm3/s and a lifetime of 0.04 ps, explaining the experimentally observed ultrafast carrier relaxation. These results highlight that engineering the surface VO chemistry will be a crucial step in optimizing Cu2O for photoelectrode applications.

氧化亚铜（Cu₂O）作为光电化学分解水的电极材料具备优异性能，但其界面处低效的电荷提取过程严重制约了实际应用性能。本研究采用杂化密度泛函理论（hybrid DFT）计算，针对实验中观测到的氧化亚铜优势(111)晶面的(√3×√3)R30°重构结构，探究了氧空位（VO）介导的载流子捕获过程。研究结果表明，这些氧空位均为双电离态，其相关缺陷态会显著抑制电子输运过程。尤为关键的是，单电荷氧空位的激发电子态在非辐射电子捕获过程中发挥核心作用：该过程的捕获系数约为10^-9 cm³/s，载流子寿命仅为0.04 ps，这一结果解释了实验中观测到的超快载流子弛豫现象。本研究结果表明，调控表面氧空位的化学性质是优化氧化亚铜光电电极应用性能的关键环节。