Light extraction from 2D materials using liquid formed micro-lenses

TL;DR

This paper introduces a micro-lens technique directly applied to 2D materials to enhance light coupling, improve photoluminescence, and protect the material, advancing the development of ultra-thin optoelectronic devices.

Contribution

The authors demonstrate a novel method of placing and tuning micro-lenses on 2D materials to improve optical performance and environmental stability.

Findings

Photoluminescence of WSe2 increased by up to 300%.

Imaging resolution nearly doubled.

Monolayer encapsulation prevented damage and degradation.

Abstract

The recent discovery of semiconducting two-dimensional materials has led to the prediction of a revolution in the field of optoelectronics, driven by the introduction of a series of new components that are just a few atoms thick. Key remaining challenges for producing practical devices from these materials lie in improving the coupling of light into and out of single atomic layers, and in making these layers robust to the influence of their surrounding environment. We present a solution to tackle both of these problems simultaneously, by deterministically placing a micro-lens directly onto the surface of these materials. These lenses are dynamically tuned to increase the coupling of light, whilst controlling chromatic aberration, before being set in place with UV light. We show that this approach enhances photoluminescence of tungsten diselenide (WSe2) monolayers by up to 300%, and nearly doubles the imaging resolution of the system. Furthermore, this solution fully encapsulates the monolayer, preventing it from physical damage and degradation in air. The optical solution we have developed could become a key enabling technology for the mass production of ultra-thin optical devices, such as quantum light emitting diodes.