Enhanced micro-LED light efficiency by optical structures on substrate

Abstract

Micro-LED displays are widely acknowledged as upcoming display innovations. However, the reduced size of micro-LED devices may compromise their light extraction efficiency. Additionally, the encapsulation structure required for the finished product of micro-LED displays leads to about a 40% loss in light intensity compared to only LED chips without encapsulation. This paper extends the EQE equation and implements a LEE secondary optics factor (the secondary optics of light extraction efficiency). We consider four different optical effects on micro-LED displays, including refraction, reflection, black matrix, and focusing. The main purpose of this paper is to study how to enhance the display-level light extraction and LEE secondary optics parameters under different conditions. We conduct optical simulations for three different LED sizes and various structures, including glue, black matrix, white glue, and microlens array. Comparing the simulation results with real experiment results, our findings show that a combination of black and white glue structures resulted in a 20% enhancement in efficiency compared to using black glue alone. Furthermore, the microlens structure led to a significant 45% enhancement in normal angle intensity compared to the protective glue structure.