High-efficiency ultrapure green organic light-emitting diodes

Abstract

To expand the color reproduction area of displays as stipulated in the Recommendation ITU-R BT.2020 for ultrahigh-definition displays, quantum dot- and perovskite-based LEDs have been intensively examined. However, it is difficult to satisfy the BT.2020 standard using quantum dot-LEDs, and the efficiency and operational stability of perovskite-based LEDs are insufficient. Herein, we report the first-ever organic LED that can emit ultrapure green light with high efficiency. The key to success is the combined use of a platinum-based pure green emitter and a boron-based host material. The optimized bottom-emitting OLED exhibited the maximum current efficiency of 84 cd A⁻¹ with CIE x–y coordinates of (0.27, 0.67). Furthermore, the CIE x–y coordinates reached (0.18, 0.74) with the use of a top-emitting structure comprising a microcavity structure and an organic capping layer. The optimized top-emitting OLED exhibited a high current efficiency of 98 cd A⁻¹ and CIE color coordinates of (0.18, 0.74) with a small angular color shift of Δxy = 0.03 at viewing angles of 0° to 60°. The newly developed ultrapure green OLED enabled the coverage of 91% of the BT.2020 standard in the CIE 1931 color gamut.