A novel intramolecular charge transfer blue fluorophor for high color stability hybrid di-chromatic white organic light-emitting diodes

A novel intramolecular charge transfer (ICT) based blue fluorophor, 5,11-di(40-dimesitylboronphenyl)indolo[3,2-b]carbazole(DDBICZ), possessing a high fluorescent quantum yield of 0.52, a high triplet energy level (2.59 eV), and an intriguing bipolar charge transporting ability, was used as a highly efficient blue fluorophor and a host for a yellow phosphor. Doping a yellow phosphor(bis(2-(3-trifluoromethyl-4-fluorophenyl)-4-methylquinolyl)(acetyl-acetonate)iridium(III) (Ir(ffpmq)₂(acac)) in the host DDBICZ, a simplified fluorescence/phosphorescence (F/P)-based hybrid white organic light-emitting diode (WOLED) with a symmetrical BYB-EML of DDBICZ (10 nm)/DDBICZ: 6 wt% Ir(ffpmq)₂(acac) (10 nm)/DDBICZ (10 nm) is demonstrated. The hybrid WOLED exhibits excellent high color stability and good color quality. Under wide operating voltage range from 5 V to 10 V, the Commission Internationale de L'Eclairage (CIE) coordinates of the hybrid WOLED only change from (0.35, 0.36) to (0.34, 0.35), with a high color rending index (CRI) of 79–81. The high color stability is due to the fact that the BYB-EML effectively offsets the change of emission intensity from different emitters caused by the shift of carrier recombination zone with the increase of voltage. In addition, the hybrid WOLED also reveals a considerable current efficiency of 24.4 cd/A. These results demonstrate that efficient F/P hybrid WOLEDs with high color stability could be achieved by such simple BYB-EML structure using single-dopant strategy.