Programme

P.7 -- Poster, VCTP-46

Date: Tuesday, 5 October 2021

Time: 08:30 - 10:00

Opto-electronic and vibrational properties of Nitrogen doped hexagonal-graphene quantum dots: A first principles study

Minh Triet Dang(1), Nguyen Vo Anh Duy(1), Nguyen Thanh Si(2), Pham Vu Nhat(2), Van An Dinh(3)

(1) School of Education, Can Tho University, 3-2 Road, Can Tho City 900000, Vietnam (2) Department of Chemistry, Can Tho University, 3-2 Road, Can Tho City 900000, Vietnam (3) Department of Precision Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan

Graphene quantum dots (GQDs) have been widely studied recently thanks to its unique optical, electrical and optoelectrical properties in applications in solar devices. Here, we present the opto-electronic properties of hexagonal graphene quantum dots and nitrogen doped graphene quantum dots using first principles method. Based on density functional theory (DFT), we investigated the changes of geometry structure, density of states, projected density of states and optical absorption of quantum dots. We have shown that by doping a nitrogen atom to hexagonal graphene quantum dots, the optical absorption of quantum dots is red-shifted towards the visible light range compared to that of the pristine graphene quantum dots, and the doped Nitrogen atom introduces a clear signature of anisotropy of the absorption spectrum. Furthermore, by artificially stretching the Carbon atoms around the doped Nitrogen atom with a distance up to 20 percent of their bond-lengths, we succesfully widen these quantum dot bandgaps from a few milli-electron Volts up to a half electron Volt, which is essential to increase the energy conversion capacity of these doped materials. These results highlight a novel approach of bottoming up the next generation of solar devices with assembled quantum dots to improve their light selectivity as well as efficiency.

Presenter: Nguyen Vo Anh Duy