Chen Yuzhong, Sun Cheng, Zhou Hongzhi, Li Jialin, Xin Wei, Xu Haiyang, Zhu Haiming
State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China.
State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, China.
J Phys Chem Lett. 2021 Oct 14;12(40):9989-9994. doi: 10.1021/acs.jpclett.1c02967. Epub 2021 Oct 7.
Because of its broad absorption and high carrier mobility, graphene has been regarded as a promising photoactive material for optoelectronics. However, its ultrashort photoexcited carrier lifetime greatly restricts the device performance. Herein, we show that by constructing a graphene/WS/MoS vertical heterostructure with a cascade electron-transfer pathway, the hot electrons in graphene under low-energy photoexcitation can efficiently transfer through WS to MoS in 180 fs, thus effectively photogating the graphene layer. Because of the spatial separation and energy barrier imposed by the WS intermediate layer which retards back electron transfer, the photocarrier lifetime in graphene is significantly prolonged to ∼382.7 ps, more than 2 orders of magnitude longer than in isolated graphene and graphene/WS binary heterostructure. The prolonged photocarrier lifetime in graphene leads to dramatically enhanced photocurrent generation and photoresponsivity. This study offers an exciting approach to control photocarrier lifetime in graphene for hot carrier devices with simultaneous broadband and high responsivity.
