Analysis and optimization on the angular color shift of RGB OLED displays

Guanjun Tan,Jiun-Haw Lee,Ruidong Zhu,Sheng-Chieh Lin,Sang-Hun Choi,Shin-Tson Wu

doi:10.1364/oe.25.033629

Abstract

Microcavites contribute to enhancing the optical efficiency and color saturation of an organic light emitting diode (OLED) display. A major tradeoff of the strong cavity effect is its apparent color shift, especially for RGB-based OLED displays, due to their mismatched angular intensity distributions. To mitigate the color shift, in this work we first analyze the emission spectrum shifts and angular distributions for the OLEDs with strong and weak cavities, both theoretically and experimentally. Excellent agreement between simulation and measurement is obtained. Next, we propose a systematic approach for RGB-OLED displays based on multi-objective optimization algorithms. Three objectives, namely external quantum efficiency (EQE), color gamut coverage, and angular color shift of primary and mixed colors, can be optimized simultaneously. Our optimization algorithm is proven to be effective for suppressing color shift while keeping a relatively high optical efficiency and wide color gamut.

Highlights

Organic light emitting diode (OLED) is emerging as a promising technology for displays [1, 2] and general lighting [3, 4]
We develop a systematic optimization algorithm, which can simultaneously optimize external quantum efficiency (EQE), color gamut coverage, and angular color shift
It describes the weakest color shift Δμ′ν′max we can obtain without sacrificing EQE and color gamut

Summary

Introduction

Organic light emitting diode (OLED) is emerging as a promising technology for displays [1, 2] and general lighting [3, 4]. In a white OLED display, red (R), green (G) and blue (B) emitter layers are stacked together to generate white pixels, and a patterned RGB color filter array is used to produce the desired colors. While in a RGB OLED display, individual red, green and blue sub-pixels are placed next to one another. Without the need of color filters, RGB OLED exhibits a lower power consumption and better color purity than white OLED. Active matrix OLED with RGB sub-pixels is gaining popularity for smartphone displays [7]. In order to improve optical efficiency and color purity, top-emitting OLED with two metallic electrodes utilizing strong microcavity resonance has been widely adopted [8, 9]. Due to Fabry–Perot resonance, the trade-offs between optical efficiency, color purity, and angular color shift inevitably exist. How to optimize the device performance becomes an urgent task

Results

Discussion

Conclusion