Spatially indirect excitons in black and blue phosphorene double layers

TL;DR

This study investigates black and blue phosphorene double layers, revealing type-II band alignment and visible-range optical absorption, and demonstrates the formation of spatially indirect excitons with potential for opto-electronic applications.

Contribution

It introduces a low-strain van-der-Waals double layer of black and blue phosphorene and shows the formation of spatially indirect excitons with full charge separation.

Findings

Type-II band alignment observed

Optical absorption in the visible range

Spatially indirect excitons with charge separation formed

Abstract

Monolayer black and blue phosphorenes possess electronic and optical properties that result in unique features when the two materials are stacked. We devise a low-strain van-der-Waals double layer and investigate its properties with ab initio many-body perturbation theory techniques. A type-II band alignment and optical absorption in the visible range are found. The study demonstrates that spatially indirect excitons with full charge separation can be obtained between two layers with the same elemental composition but different crystalline structure, proving the system interesting for further studies where dipolar excitons are important and for future opto-electronic applications.