Tripling Light Conversion Efficiency of μLED Displays by Light Recycling Black Matrix

Xiang Zhang,Sheng Xu,Yun Ye,Anlan Chen,Enguo Chen,Qun Yan,Junhu Cai,Jie Sun,Yuanyuan Ye,Tailiang Guo,Tao Yang

doi:10.1109/jphot.2022.3148241

Abstract

Quantum-dot color conversion film (QDCCF) with a partitioned black matrix (BM) realizes effective color generation with low crosstalk for micro-light-emitting diode (μLED) displays. However, this traditional BM seriously deteriorates light conversion efficiency (LCE) of QD converted μLED displays due to its absorption energy loss. In this paper, a novel internal and external reflective black matrix (IERBM) is proposed to improve the LCE and blue light utilization (BLU) by light recycling and reuse. Based on the IERBM structural optimization, the LCE can be respectively improved by 3.39× and 2.74× for red and green QDCC sub-pixels, and the BLU can be effectively increased by 1.11×. Accurate white balance and high color uniformity are achieved by this μLED display. Meanwhile, both the crosstalk of 1.72% and the color gamut of 89.8% Rec. 2020 are comparable with traditional absorptive BM. It is also found that the proposed IERBM has the potential to weaken μLED's sidewall effect. This work may open up a new technological route for improving the optical performance in advanced self-emissive displays.

Highlights

COLOR conversion is a dominating technique for realizing full-color displays [1,2,3]
Shrinkage in pixel size from conventional LED into μLED brings about dramatic decrease of light conversion efficiency (LCE)
Existing LCE improvement approaches mainly focus on the Quantum-dot color conversion film (QDCCF) and μLED structures, whereas the black matrix has not been taken into consideration yet

Summary

Introduction

COLOR conversion is a dominating technique for realizing full-color displays [1,2,3]. White light from the backlight is firstly generated by blue LEDs and the capped yellow phosphors, and three primary colors are separated by an absorptive color filter [4,5,6]. The combination of phosphors and color filter inevitably brings narrow color gamut and low optical efficiency, which is antithetical to the requirements of next-generation displays [7,8]. For self-luminous displays, such as organic light-emitting diode (OLED) or micro-light-emitting diode (μLED), the QDs can be patterned and pixelated as a color conversion layer aligned with excitation sub-pixels to improve the efficiency and color gamut [17,18]

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