Enhanced Light Extraction From Green Quantum Dot Light-Emitting Diodes by Attaching Microstructure Arrayed Films

Abstract

In this study, microstructure arrayed films, such as microlens and microprism arrayed sheets, were introduced to the front side of quantum dot light-emitting diodes (QLEDs) to enhance the extraction efficiency of the QLEDs without fabricating complex micro/nano-structures directly on the substrate of the QLEDs. Additionally, the optical properties of the microlens and microprism film-attached QLEDs were compared with those of conventional QLEDs (without microstructures). Conventional QLEDs were fabricated as a reference device with gradient-thick shell green emitting CdSe@ZnS/ZnS quantum dots (QDs). The microlens-attached QLEDs have a high current efficiency (CE) of 31.3 cd/A, an external quantum efficiency (EQE) of 7.9% at 7 V, and a bright luminescence value of 99 350 cd/m(2) at 10 V. The CE, EQE, and luminescence values of the microlens-attached QLEDs are 1.47, 1.41, and 1.57 times higher than those of conventional QLEDs, respectively. The EL spectra and the color coordinates of the QLEDs only changed very slightly by adding microstructured arrays to the QLEDs.