Room Temperature Micro-Photoluminescence Studies of Colloidal WS2 Nanosheets

TL;DR

This study demonstrates room temperature micro-photoluminescence in colloidal WS2 nanosheets, revealing their high optical quality and stability, and highlights their potential as solution-processable 2D semiconductors.

Contribution

First demonstration of room temperature micro-photoluminescence in colloidal WS2 nanosheets with comparable properties to exfoliated monolayers.

Findings

Colloidal WS2 nanosheets exhibit both mono- and multilayer photoluminescence.

High air-stability of colloidal WS2 nanosheets is observed.

Photodegradation under laser excitation is a challenge for future work.

Abstract

Wet-chemical syntheses for quasi two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as promising methods for straightforward solution-processing of these materials. However, photoluminescence properties of colloidal TMDs are virtually unexplored due to the typically non-emitting synthesis products. In this work, we demonstrate room temperature micro-photoluminescence of delicate ultrathin colloidal WS2 nanosheets synthesized from WCl6 and elemental sulfur in oleic acid and oleylamine at 320 {\deg}C for the first time. Both, mono- and multilayer photoluminescence are observed, revealing comparable characteristics to exfoliated TMD monolayers and underpinning the high quality of colloidal WS2 nanosheets. In addition, a promising long-term air-stability of colloidal WS2 nanosheets is found and the control of photodegradation of the structures under laser excitation is identified as a challenge for further advancing nanosheet monolayers. Our results render colloidal TMDs as easily synthesized and highly promising 2D semiconductors with optical properties fully competitive with conventionally fabricated ultrathin TMDs.