Light emission from the layered metal 2H-TaSe2 and its potential applications

Abstract

Conventional metals, in general, do not exhibit strong photoluminescence. 2H-TaSe2 is a layered transition metal dichalcogenide that possesses metallic property with charge density wave characteristics. Here we show that 2H-TaSe2 exhibits a surprisingly strong optical absorption and photoluminescence resulting from inter-band transitions. We use this perfect combination of electrical and optical properties in several optoelectronic applications. We show a sevenfold enhancement in the photoluminescence intensity of otherwise weakly luminescent multi-layer MoS2 through non-radiative resonant energy transfer from TaSe2 transition dipoles. Using a combination of scanning photocurrent and time-resolved photoluminescence measurements, we also show that the hot electrons generated by light absorption in TaSe2 have a rather long lifetime unlike conventional metals, making TaSe2 an excellent hot electron injector. Finally, we show a vertical TaSe2/MoS2/graphene photodetector demonstrating a responsivity of >10 AW−1 at 0.1 MHz—one of the fastest reported photodetectors using MoS2.