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.

Synthesis and fluorescence properties of 7-hydroxy-3-(2-pyridyl)coumarin derivatives

“…Similar phenomena were reported by Khilya et al [24] and Azuma et al [25]. It was well known that electron-withdrawing groups at the 3-position and electron-donating groups at the 7-position have been shown to enhance the fluorescence intensity of coumarins [6,15,26]. Although the electron-donating ability of hydroxy group is larger than that of the alkoxy and benzyloxy groups, there are intermolecular interactions between HPC molecules and between HPC molecules and solvent molecules via hydrogen bondings, which causes the fluorescence of HPC to be quenched.…”

“…The coumarin derivatives substituted at the 7-position with electron-releasing moieties and at the 3-position with electron-withdrawing groups are a class of D-A structural molecules and exhibit strong emissions [6,14,15]. The search for new multifunctional coumarin derivatives which can efficiently act as fluorescence dyes for various potential applications has been an active area of modern research [16][17][18][19].…”

A New Orange-Light-Emitting Materials Based on (N-naphthyl)-1,8-naphthalimide for OLED Applications

“…For realization of full-color, organic materials emitting the three primary colors of red, green, and blue with high efficiency, good color purity are required [6][7][8]. Recently, much attention has been paid to OLEDs based on red and orange emitting materials [9].…”

Aggregation-induced delayed fluorescence from phenothiazine-containing donor–acceptor molecules for high-efficiency non-doped organic light-emitting diodes

“…1 Although most organic fluorophores are highly luminescent in dilute solutions, their luminescence is generally weakened or quenched in the solid state via bimolecular recombination and energy transfer to non-luminescent impurities, which results in a substantial energy loss in the OLEDs. [2][3][4][5] This problem is typically circumvented by dispersing the fluorophores in wide bandgap host materials via precise co-evaporation processes; however, this approach requires complex manufacturing procedures. Thus, highly luminescent solid-state fluorophores are highly desirable for simplifying the device structure and the fabrication process.…”