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.

Cu2O作为光电化学水分解电极材料，因其优异的物理特性而备受青睐，然而其实际性能却因界面电荷提取效率低下而受到严重制约。通过采用混合密度泛函理论计算，本研究对实验观察到的以(√3×√3)R30°重构的(111)主导表面的氧空位（VO）捕获载流子过程进行了深入研究。研究表明，这些VO处于双离子化状态，且与其相关的缺陷态显著抑制了电子传输。特别是，单电荷VO的激发电子态在非辐射电子捕获过程中发挥着至关重要的作用，其捕获系数约为10^-9 cm3/s，寿命为0.04 ps，这解释了实验观察到的超快载流子弛豫现象。这些发现凸显了，通过调控表面VO化学性质将是优化Cu2O光电极应用性能的关键步骤。