Highly efficient single- and multi-emission-layer fluorescent/phosphorescent hybrid white organic light-emitting diodes with ∼20% external quantum efficiency

Abstract

A blue fluorophore of N,N-diphenyl-4′′-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1′:4′,1′′-terphenyl]-4-amine (BBPI) was utilized as the blue fluorescent emitter and the host of a phosphorescent emitter to fabricate highly efficient fluorescent/phosphorescent (F/P) hybrid white organic light-emitting diodes (WOLEDs) in a single- or multi-emission-layer architecture. For the single-emission-layer WOLEDs consisting of only the blue emitter BBPI and yellow complementary phosphorescent emitter PO-01 in the emission layer, a maximal current efficiency (CE) of 49.1 cd A⁻¹, power efficiency (PE) of 52.0 lm W⁻¹, and external quantum efficiency (EQE) of 16.3% were achieved by modulating the dopant concentration, indicating efficient singlet and triplet exciton separation and utilization ability in the emission layer. An improved EQE of 17.1%, broader spectral coverage, and higher color rendering index (CRI) were achieved by inserting a non-doped blue emission layer of BBPI and a green emission layer of CBP:Ir(PPy)₃. A further improved EQE of up to 19.7% could be achieved when an orange-red phosphorescent emitter PQ₂Ir was used instead of PO-01, and it is one of the best reported values for the F/P hybrid WOLEDs.