Dual Partial Dye Doping for Chromaticity Tuning and Performance Enhancement of White OLEDs

In general, a guest dopant is doped into a single host matrix for white-light emission with two complementary colors. In this work, however, we have fabricated a white organic light-emitting diode (WOLED) based on dual partial dye doping in which a guest dopant is partially doped into two different host emitters; namely, orange-red emitting 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminos-tyryl)-4H-pyran (DCM) is partially doped into both blue-emitting 4, 4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl (DPVBi) and green-emitting Tris-(8-hydroxyquinoline) aluminum (Alq₃). We demonstrate that dual partial dye doping allows us to finely tune the Commission Internationale d'Eclairage (CIE) chromaticity coordinates to the equienergy white point (x = 0.33, y = 0.33). In addition, it enhances device performance further, compared to WOLEDs based on DCM partially doped into a single host matrix (either DPVBi or Alq₃). Moreover, the dual partial doping scheme is shown to provide a way of suppressing the self-quenching effect (singlet-singlet annihilation). For a systematic study, we have implemented a comprehensive numerical model and performed simulations of the OLED structure, providing a clear understanding with regard to the underlying physics of OLEDs. We also carry out an investigation of the effects of key design parameters such as the doped layer position and thickness and dye.