2015/11/10 by F. Withers, Freddie Withers, Osvaldo Del Pozo-Zamudio +29 · 275 citations
Chemistry · Materials Science · Physics and Astronomy · #2D Materials and Applications #Band gap #Chemistry #Condensed matter physics #Exciton #Graphene #Graphene research and applications #Heterojunction #MXene and MAX Phase Materials #Materials science #Monolayer #Nanotechnology #Optics #Optoelectronics #Physics #Quantum efficiency #Quantum tunnelling #Quantum well #Semiconductor #Transition metal #Tungsten #Tungsten diselenide #cond-mat.mes-hall
paper · pdf · doi:10.1021/acs.nanolett.5b03740
published in Nano Letters 15(12), 8223-8228 (American Chemical Society)
openalex publication_date 2015/11/10 · arxiv created 2015/11/19 · arxiv updated 2015/11/20 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Monolayers of molybdenum and tungsten dichalcogenides are direct bandgap semiconductors, which makes them promising for optoelectronic applications. In particular, van der Waals heterostructures consisting of monolayers of MoS2 sandwiched between atomically thin hexagonal boron nitride (hBN) and graphene electrodes allows one to obtain light emitting quantum wells (LEQWs) with low-temperature external quantum efficiency (EQE) of 1%. However, the EQE of MoS2- and MoSe2-based LEQWs shows behavior common for many other materials: it decreases fast from cryogenic conditions to room temperature, undermining their practical applications. Here we compare MoSe2 and WSe2 LEQWs. We show that the EQE of WSe2 devices grows with temperature, with room temperature EQE reaching 5%, which is 250× more than the previous best performance of MoS2 and MoSe2 quantum wells in ambient conditions. We attribute such different temperature dependences to the inverted sign of spin-orbit splitting of conduction band states in tungsten and molybdenum dichalcogenides, which makes the lowest-energy exciton in WSe2 dark.