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Excitonic light emitting devices based on two dimensional transition metal dichalcogenides
October 25, 2019 @ 3:00 pm - 4:00 pm
Date/Time: 25th October 2019, 1500 hrs
Venue: ESB 244 (Electrical Engineering Seminar Hall)
Speaker: Ankit Arora (EE16D025)
Guides: Prof. Ananth Krishnan (EE) and Prof. M. S. Ramachandra Rao (PH)
Two-dimensional transition metal dichalcogenides (TMDs), such as MoS2 and WSe2 form a class of atomically thin, direct band semiconductors, with the bandgaps in the visible or near Infrared (NIR). These materials exhibit strong light-matter interaction with stable excitons even at room temperature and are potential candidates for various applications in optoelectronics. In this work, we propose to demonstrate an on-chip, electrically pumped, excitonic light emitting device, functional at room temperature using TMDs as active material.
In this talk, the excitonic landscape of MoS2 and WSe2 in monolayer (1L), bilayer (BL) and multilayer (ML) systems will be discussed. Different excitonic configurations were observed when these material systems were characterized using photoluminescence spectroscopy. These excitations were experimentally tuned using stacking angle in BL system and plasmon induced effects in case of 1L and ML systems. In order to extend the functionality of these materials, ML-MoS2/ZnO heterostructures (HS) were fabricated. It was observed that when gold nanoparticles were introduced at the MoS2-ZnO interface, the emission intensities were enhanced. For MoS2 flakes of thickness > 200 nm, these HS exhibited room temperature, continuous wave, random lasing in NIR region. This was attributed to enhanced multiple scattering and exciton-plasmon coupling because of gold nanoparticles. Based on the understanding from these experiments, the possibility of an on-chip electrically pumped light emitting device will be discussed.