摘要
Two-dimensional(2D)InSe and WS2 exhibit promising characteristics for optoelectronic applications.However,they both have poor absorption of visible light due to wide bandgaps:2D InSe has high electron mobility but low hole mobility,while 2D WS2 is on the contrary.We propose a 2D heterostructure composed of their monolayers as a solution to both problems.Our first-principles calculations show that the heterostructure has a type-Ⅱband alignment as expected.Consequently,the bandgap of the heterostructure is reduced to 2.19 eV,which is much smaller than those of the monolayers.The reduction in bandgap leads to a considerable enhancement of the visible-light absorption,such as about fivefold(threefold)increase in comparison to monolayer InSe(WS2)at the wavelength of 490 nm.Meanwhile,the type-Ⅱ band alignment also facilitates the spatial separation of photogenerated electron-hole pairs;i.e.,electrons(holes)reside preferably in the InSe(WS2)layer.As a result,the two layers complement each other in carrier mobilities of the heterostructure:the photogenerated electrons and holes inherit the large mobilities from the InSe and WS2 monolayers,respectively.
Two-dimensional（2D）InSe and WS2 exhibit promising characteristics for optoelectronic applications.However,they both have poor absorption of visible light due to wide bandgaps:2D InSe has high electron mobility but low hole mobility,while 2D WS2 is on the contrary.We propose a 2D heterostructure composed of their monolayers as a solution to both problems.Our first-principles calculations show that the heterostructure has a type-Ⅱband alignment as expected.Consequently,the bandgap of the heterostructure is reduced to 2.19 eV,which is much smaller than those of the monolayers.The reduction in bandgap leads to a considerable enhancement of the visible-light absorption,such as about fivefold（threefold）increase in comparison to monolayer InSe（WS2）at the wavelength of 490 nm.Meanwhile,the type-Ⅱ band alignment also facilitates the spatial separation of photogenerated electron-hole pairs;i.e.,electrons（holes）reside preferably in the InSe（WS2）layer.As a result,the two layers complement each other in carrier mobilities of the heterostructure:the photogenerated electrons and holes inherit the large mobilities from the InSe and WS2 monolayers,respectively.
基金
Supported by the National Natural Science Foundation of China under Grant Nos 11404013,11474012,11364030,61622406,61571415,51502283 and 11605003
the National Key Research and Development Program of China under Grant No2017YFA0206303
the MOST of China,and the 2018 Graduate Research Program of Beijing Technology and Business University
