Anisotropy of the Optical Properties of Pentacene:Black Phosphorus Interfaces

TL;DR

This study investigates the anisotropic optical properties of pentacene on black phosphorus interfaces using advanced first-principles calculations, revealing direction-dependent excitonic behavior relevant for surface passivation.

Contribution

It introduces a computational scheme to analyze interface excitons and demonstrates the anisotropic charge-transfer exciton formation on BP with pentacene monolayers.

Findings

Charge-transfer exciton forms along the armchair direction.

Optical anisotropy is modulated by interface orientation.

Provides a benchmark for future experimental and computational studies.

Abstract

Black phosphorus (BP) is a layered material with anisotropic properties. We study interfaces formed by a pentacene monolayer adsorbed on monolayer BP, a prototypical system for BP surface passivation. We place the pentacene monolayer along the zigzag and armchair directions of the BP substrate, respectively, to examine the anisotropy of the heterogeneous interfaces. We perform first-principles $GW$ plus Bethe-Salpeter equation ($GW$-BSE) calculations to determine the quasiparticle and optical properties. To quantitatively analyze the anisotropy of the optical properties, we develop a general computational scheme to decompose the interface excitons into different contributions. We find a distinct charge-transfer exciton formed when the monolayer pentacene is placed along the armchair direction, and discuss how the anisotropy of each component is modulated by the interface. Our results shine a light on the understanding of the BP surface passivation via molecular adsorption and provide a benchmark for future experimental and computational studies.