Title: Electronic and Optical Properties of Two-Dimensional \alpha-PbO from First Principles

Speaker: Dr. Suvadip Das, University of Michigan

Abstract: Functional two dimensional materials such as MoS2 and other transition metal dichalcogenides (TMDs) are promising for advanced atomically thin electronic and optoelectronic devices, such as light emitting diodes (LEDs), ultrathin solar cells, and valleytronic devices. The search for oxidation-resistant novel two-dimensional materials for energy application beyond transition metal dichalcogenides (TMDs) has motivated us to explore the IV-VI Group material α-PbO. Recently, atomic layers of α-PbO have been successfully grown for the first time using micromechanical and sonochemical exfoliation. We performed first-principles calculations based on density functional theory and many-body perturbation theory to investigate the electronic and optical properties (utilizing the GW and BSE methodology) of monolayer, bilayer, and bulk litharge α-PbO1, including spin-orbit coupling effects. A pronounced van Hove singularity in the valence band of the few-layer structures suggests it becomes a multiferroic two dimensional material upon hole doping. Further, strong excitonic binding energy was observed in monolayers of newly exfoliated α-PbO due to confinement. The α-PbO monolayer is nearly transparent in the visible and near UV, and absorbs strongly in the vacuum UV range, which is promising for solar-blind UV photodetectors. Our results demonstrate that 2D α-PbO exhibits a synergy of desirable electronic and optical properties with oxidation resistance and possible multifunctionality.

(1) Das, S.; Shi, G.; Sanders, N.; Kioupakis, E. Electronic and Optical properties of Two-Dimensional α-PbO from First Principles. Chem. Mater. 2018, 30, 20, 7124-7129.