Session: 17-01-01: Research Posters
Paper Number: 145103
145103 - Carrier Controllability in Two-Dimensional Transition Metal Dichalcogenides
There has been a lot of focus on two-dimensional (2D) transition metal dichalcogenide (TMDC) materials for their potential use in optoelectronic applications. This is because their band gap shifts from indirect to direct as they decrease in thickness from multilayer to monolayer. Photochromic molecules switch between two different isomers, with distinct energy levels, when exposed to ultraviolet (UV) or visible light. Recent research has investigated the use of photochromic molecules for controlling the carrier (electrons and holes) transport from and to 2D TMDC semiconductors. This study numerically explored the feasibility of using photochromic molecules to control the electrical and optical properties of 2D TMDC monolayers. By aligning the energy levels of the photochromic isomer with the band gap of the TMDC monolayers, carriers can be directed towards the molecules, reducing exciton density in the TMDC. This reduced optical response can be reversed by inducing the molecules to switch back to their original isomer. Therefore, it is crucial to find suitable combinations of photochromic molecules and TMDC monolayers for achieving photo-switchable properties. To identify these pairs, density functional theory (DFT) calculations were employed to examine the electronic structures and density of states of each photochromic-TMDC combination. The DFT calculations were performed using Vienna Ab-initio Simulation Package with the projector augmented wave method. Electron exchange and correlation were treated with the generalized gradient approximation in the form of Perdew-Burke-Ernzerhof functional. The van der Waals interaction was described by adding a dispersion correction using DFT-D2 method. The photochromic-TMDC combinations consisted of different TMDC monolayers including molybdenum diselenide (MoSe2), molybdenum disulfide (MoS2), and tungsten diselenide (WSe2) with various photochromic molecules including azobenzene, two kinds of spiropyran (spiropyran [C19H18N2O3] and spiropyran-S [C23H20N2O3S]), and three kinds of diarylethene (diarylethene (DAE)-2ethyl, DAE-5ethyl, and DAE 5-methyl). The results show that all the tested DAE molecules with either MoSe2 or WSe2 monolayers have controllable exciton density when exposed to UV or visible light. MoS2 also showed controllable exciton density with DAE molecules, except DAE 5-methyl. In addition, the WSe2 monolayer with azobenzene can also exhibit a controllable optical response through the transfer of holes. However, the MoSe2 monolayers with azobenzene or spiropyran-S do not exhibit photo-switchable behavior, but WSe2 monolayer with spiropyran-S exhibits controllable exciton density.
Presenting Author: Henry Fischer University of St Thomas
Presenting Author Biography: Henry is an undergraduate student at the department of mechanical engineering at the university of St Thomas.
Authors:
Henry Fischer University of St ThomasSrajan Pillai University of St Thomas
Jeong Ho You University of St Thomas
Sewon Park Purdue University
Jong Hyun Choi Purdue University
Carrier Controllability in Two-Dimensional Transition Metal Dichalcogenides
Paper Type
Poster Presentation