Slow cooling and efficient extraction of C-exciton hot carriers in MoS2 monolayer

Lei Wang, Zhuo Wang, Hai Yu Wang, Gustavo Grinblat, Yu-Li Huang, Dan Wang, Xiao-Hui Ye, Xian-Bin Li, Qiaoliang Bao, Andrewthye Shen Wee, Stefan A. Maier, Qi-Dai Chen, Min-Lin Zhong, Cheng-Wei Qiu, Hong-Bo Sun

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In emerging optoelectronic applications, such as water photolysis, exciton fission and novel photovoltaics involving low-dimensional nanomaterials, hot-carrier relaxation and extraction mechanisms play an indispensable and intriguing role in their photo-electron conversion processes. Two-dimensional transition metal dichalcogenides have attracted much attention in above fields recently; however, insight into the relaxation mechanism of hot electron-hole pairs in the band nesting region denoted as C-excitons, remains elusive. Using MoS22 monolayers as a model two-dimensional transition metal dichalcogenide system, here we report a slower hot-carrier cooling for C-excitons, in comparison with band-edge excitons. We deduce that this effect arises from the favourable band alignment and transient excited-state Coulomb environment, rather than solely on quantum confinement in two-dimension systems. We identify the screening-sensitive bandgap renormalization for MoS2 monolayer/graphene heterostructures, and confirm the initial hot-carrier extraction for the C-exciton state with an unprecedented efficiency of 80%, accompanied by a twofold reduction in the exciton binding energy.

Original languageEnglish
Article number13906
Number of pages8
JournalNature Communications
Publication statusPublished - 5 Jan 2017

Cite this

Wang, L., Wang, Z., Wang, H. Y., Grinblat, G., Huang, Y-L., Wang, D., Ye, X-H., Li, X-B., Bao, Q., Wee, A. S., Maier, S. A., Chen, Q-D., Zhong, M-L., Qiu, C-W., & Sun, H-B. (2017). Slow cooling and efficient extraction of C-exciton hot carriers in MoS2 monolayer. Nature Communications, 8, [13906].