Ultrafast formation of interlayer hot excitons in atomically thin MoS2/WS2 heterostructures

• Published in: Nature communications Vol. 7; no. 1; p. 12512
• Main Authors: Chen, Hailong, Wen, Xiewen, Zhang, Jing, Wu, Tianmin, Gong, Yongji, Zhang, Xiang, Yuan, Jiangtan, Yi, Chongyue, Lou, Jun, Ajayan, Pulickel M., Zhuang, Wei, Zhang, Guangyu, Zheng, Junrong
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 19.08.2016; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/119; 639/766/1130; 639/925/357/1018; Chemistry; Electrons; Energy; Geometry; Humanities and Social Sciences; Localization; multidisciplinary; Physics; Science; Science (multidisciplinary); Single crystals; Beijing China; United States > US; China; Texas
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms12512

Van der Waals heterostructures composed of two-dimensional transition-metal dichalcogenides layers have recently emerged as a new family of materials, with great potential for atomically thin opto-electronic and photovoltaic applications. It is puzzling, however, that the photocurrent is yielded so efficiently in these structures, despite the apparent momentum mismatch between the intralayer/interlayer excitons during the charge transfer, as well as the tightly bound nature of the excitons in 2D geometry. Using the energy-state-resolved ultrafast visible/infrared microspectroscopy, we herein obtain unambiguous experimental evidence of the charge transfer intermediate state with excess energy, during the transition from an intralayer exciton to an interlayer exciton at the interface of a WS 2 /MoS 2 heterostructure, and free carriers moving across the interface much faster than recombining into the intralayer excitons. The observations therefore explain how the remarkable charge transfer rate and photocurrent generation are achieved even with the aforementioned momentum mismatch and excitonic localization in 2D heterostructures and devices. Van der Waals heterostructures, fabricated via vertical stacking of two-dimensional materials, hold promise for opto-electronic applications. Here, the authors study the exciton-assisted charge transfer mechanisms occurring in a WS 2 /MoS 2 heterojunction via ultrafast microspectroscopy.