Excitonic solar cells based on van der Waals heterojunctions of Janus III-VI chalcogenide monolayers.

We construct the two-dimensional (2D) excitonic solar cells based on type II vdW heterojunctions of Janus III-VI chalcogenide monolayers and investigate the performance of the device using the first principle. The calculated solar energy absorbance of In2SSe/GaInSe2 and In2SeTe/GaInSe2 heterojunctions is the order of 105 cm-1. The predicted photoelectric conversion efficiency of the In2SeTe/GaInSe2 heterojunction can reach up to 24.5%, which compares favorably with other previously studied 2D heterojunctions. The excellent performance of In2SeTe/GaInSe2 heterojunction originates from the fact that the built-in electric field at the interface of In2SeTe/GaInSe2 promote the flow of the photogenerated electrons. The results suggest that 2D Janus Group-Ⅲ chalcogenide heterojunction can be a good candidate for new optoelectronic nanodevices.&#xD.