A robust yellow-emitting metallophosphor with electron-injection/- transporting traits for highly efficient white organic light-emitting diodes

With the aim of endowing triplet emitters in the development of organic light-emitting devices (OLEDs) with electron-injection/-transporting (EI/ET) features, the phenylsulfonyl moiety was introduced into the phenyl ring of a 2-phenylpyridine (Hppy) ligand and the yellow phosphorescent heteroleptic iridium(III) complex 1 was developed. It was shown that the SO2Ph unit could provide EI/ET character to 1, as indicated from both electrochemical and computational data. Complex 1 is a promising yellow-emitting material for both monochromatic OLEDs and white OLEDs (WOLEDs). The outstanding electronic traits associated with 1, coupled with careful device design, afforded very attractive electroluminescent performances for two-element WOLEDs, including a low turn-on voltage of less than 3.7 V, a maximum brightness of 48 000 cd m-2, an external quantum efficiency of 13.0 %, a luminance efficiency of 34.7 cd A-1, and a power efficiency of 24.3 Lm W-1. In addition, a good color rendering index (CRI) of about 74, a stable white color with a Commission Internationale de L'Eclairage (CIEx,y) variation of Δ(x, y)<±(0.02, 0.02), and a correlated color temperature higher than 5130 K were obtained. These encouraging results indicate the potential of these WOLEDs as good candidates for warm indoor lighting sources, as well as the critical contribution of such key EI/ET properties to triplet emitters to advance new OLED research. The future's white: A yellow-emitting IrIIIphosphor with electron-injection/-transporting (EI/ET) features (see figure) is employed for the first time to develop highly efficient white organic light-emitting diodes (WOLEDs).