Enhancing the brightness of quantum dot light emitting diodes by multilayer hetero-structures

Abstract

Quantum dots (QDs) show great promise for use in nanotechnology, owing to their high quantum efficiency, color tenability, narrow emission, and high luminescence efficiency. As a new generation of light emitting device (LED), QD-LEDs have attracted a great deal of attention in displays and lighting. In order to meet the commercial requirements, the brightness of QD-LEDs need to be further improved. In this work, we propose multilayer hetero-structures on a SiO2 substrate, which provides multiple reflective bands with the very high reflective efficiency nearly up to 100%. Electric field distributes mostly in the superficial layer. The proposed structure provides highly multiband reflection covering the emission peaks of QDs in LEDs, so it can enhance QDs' fluorescence and enhance the brightness of QD-LEDs eventually. We investigated four typical emission wavelengths, mainly aimed at red QD-LEDs and infrared QD-LEDs, which correspond to the applications of displays, infrared illumination, optical communication and so on. The total reflection bands can be adjusted according to practical requirements by tuning the thickness of per layer. One fabrication procedure can be used for different kinds QDs or the same kind QD with different sizes without changing their processing properties. The proposed structure has fewer flat layers compared to one-dimensional photonic crystals, which leads to lower cost and easier fabrications.