Stable and efficient fluorescent red and green dyes for external and internal conversion of blue OLED emission

Abstract

We have synthesized a series of diphenylamine-substituted coumarin, (dicyanomethylene)-pyran, and benzophenoxazone dyes and report on their optical and electroluminescent properties, thermal and photooxidative stabilities, and potential as red and green dopants for organic light-emitting diode (OLED) displays or down-conversion fluorescent dyes for external color-converters. Incorporation of the bulky phenyl groups in these dyes delays the onset of concentration quenching when they are dissolved in polymer films. Their improved photoluminescent efficiency and photooxidative stability make them excellent candidates for external color-conversion. The improved electroluminescence and power efficiencies and enhanced thermal stability of 3-(2′ -benzimidazolyl)-7-(diphenylamino)-2H-1-benzopyran-2-one (C7S) as well as its Commission Internationale d'Eclairage (CIE) coordinates suggests its use as a green dopant in OLED devices.