Enhanced Optical Gain from Photoactivated Colloidal Quantum Wells

Abstract

Cadmium chalcogenide colloidal quantum wells (CQWs) are a unique class of optical gain materials that can be precisely engineered in terms of thickness and composition at the atomic level using colloidal atomic layer deposition (c-ALD). However, the atomic layer deposition is typically performed at room temperature, resulting in low emission efficiency and the need for additional thermal annealing. In this study, ultraviolet (UV) illumination is used to treat the CQWs prepared using c-ALD and a significant improvement in their photoluminescence is observed, with an irreversible 79-fold increase. Furthermore, the lasing threshold is reduced to two-thirds of the untreated samples, enabling whispering gallery mode lasing from the CQW in solution. This research demonstrates an efficient and convenient method for boosting the emission from the CQWs and highlights the advantages of CQWs as optical gain media that can be engineered with atomic precision.