title: Up to 100% Formation Ratio of Doublet Exciton in Deep-Red Organic Light-Emitting Diodes Based on Neutral π-Radical.
abstract: In a neutral π-radical-based organic light-emitting diode (OLED), although the emission comes from the doublet excitons and their transition to the ground state is spin-allowed, the upper limit of internal quantum efficiency (IQE) is not clear, 50% or 100%? In this work, the deep-red OLEDs based on a neutral π-radical were fabricated. Up to 100% doublet exciton formation ratio was obtained through rational designing device structure and host-guest doping system. This indicates the IQE of neutral π-radical-based OLEDs will reach 100% if the nonradiative pathways of radicals can be suppressed. The maximum external quantum efficiency of the optimized device is as high as 4.3%, which is among the highest values of deep-red/near-infrared OLEDs with nonphosphorescent materials as emitters. Our results also indicate that using partially reduced radical mixture as emitter may be a way to solve aggregation-caused quenching in radical-based OLEDs.
authors.affiliation: State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University , Qianjin Avenue 2699, Changchun 130012, P.R. China.
authors.forename: Ablikim
authors.initials: A
authors.lastname: Obolda
authors.affiliation: State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University , Qianjin Avenue 2699, Changchun 130012, P.R. China.
authors.forename: Xin
authors.initials: X
authors.lastname: Ai
authors.affiliation: State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University , Qianjin Avenue 2699, Changchun 130012, P.R. China.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University , Qianjin Avenue 2699, Changchun 130012, P.R. China.
authors.forename: Feng
authors.identifier: http://orcid.org/0000-0001-5236-3709
authors.initials: F
authors.lastname: Li
keywords: deep-red OLEDs; doublet exciton; internal quantum efficiency; neutral π-radical; open-shell molecule