Unraveling the Origin of Low Optical Efficiency for Quantum Dot White Light-Emitting Diodes From the Perspective of Aggregation-Induced Scattering Effect

Abstract

Quantum dots (QDs) are promising materials for various optoelectronic applications. However, the efficiency of QD white light-emitting diodes (QD-white-LEDs) is not at the desired level, particularly when the QD concentration in the silicone matrix is high and the corresponding mechanism has not been fully elucidated. In this study, we experimentally and theoretically investigated the aggregation-induced scattering (AIS) effect of QDs in silicone and unraveled the origin of low efficiency for QD-white-LED devices. Three-dimensional finite-difference time domain and ray tracing simulations were carried out to establish the AIS model for QDs. Results indicate that the AIS effect is stronger for higher QD concentrations and leads to a larger effective aggregate size (EAS), which was confirmed by comparing with the experimental results of QD-silicone films. Furthermore, we found that the AIS effect causes a significant reduction in the radiant efficiencies of QD-white-LEDs when the EAS exceeds 50 particles, which is validated by fabricated devices. According to the spectral energy analysis, the low efficiency of QD-white-LEDs can be attributed to a strong AIS effect at high QD concentrations, causing severe backscattering and reabsorption loss. This study is also important for nondestructive testing the degree of aggregation demonstrated by QDs in a silicone matrix and for precisely modeling QD-white-LEDs.