39.1: Invited Paper: High Performance Red and Green Phosphorescent Emitters Suitable for BT.2020 Color Gamut

Abstract

We developed a novel, deep red phosphorescent emitter (DRD‐II), with a photoluminescence (PL) spectrum as narrow as 30 nm at full‐width‐half‐maximum (FWHM). A top‐emission red organic light emitting device (OLED) built with DRD‐II achieved a current efficiency (CE) of 59 cd/A, operating voltage of 3.2 V and lifetime to 95% of initial brightness (LT95) over 20,000 h at a drive current of 10 mA/cm2 with CIE (x, y) = (0.707, 0.293). We also developed a green phosphorescent organic emitter (GD) whose PL spectrum shows FWHM of 30 nm and peak wavelength (λmax) of 523 nm. A top‐emission green OLED was built with this GD and reached CE of 171 cd/A, voltage of 3.3 V and LT95 > 1,300 h at 10 mA/cm2 with CIE (x, y) = (0.169, 0.777). This is, to our knowledge, the best efficiency and lifetime combination ever reported for a green OLED at this CIE y. Combining these red and green emitters with a commercial blue OLED at CIE (0.131, 0.046), we are able to cover 97% of the BT.2020 color gamut. Through optical simulation, we also provide guidance to further improve red and green emitters. It is found that a red emitter with smaller FWHM not only maintains saturated color at a shorter peak wavelength but also gains luminance efficiency owing to the elimination of longer wavelengths. On the other hand, the simulation demonstrates that it is indeed challenging for phosphorescent green emitters to satisfy BT.2020. Nevertheless, it is possible to reach CIE y = 0.785 with a narrow line shape and minimal shoulder peak.