Highly efficient nondoped blue electroluminescence with an EQE greater than 6.0% based on a phenothiazine donor with hybridized local and charge-transfer excited state

Abstract

Excited state characteristics of a new generation of organic luminescent materials play a key role in determining their luminescent properties. As a special excited species, the hybridized local and charge-transfer (HLCT) excited state is a promising strategy to achieve blue emission and high photoluminescence quantum yield. Herein, a novel donor-acceptor fluorophore, namely 2-phenyl-5-(10-(4-(1,2,2-triphenylvinyl)phenyl)-10H-phenothiazin-3-yl)-1,3,4-oxadia-zole (TPEPO), is designed and synthesized as an efficient blue organic light-emitting diode (BOLED) material. Remarkably, the external quantum efficiencies of the nondoped device with TPEPO as an emitter was as high as 6.62% and radiative exciton ratio was also high, i.e., approximately 36%–55%, indicating that the developed BOLED exhibits the highest efficiency that has been reported so far for a BOLED based on phenothiazine as the donor material. This work provides a comprehensive understanding of the relation between the excited state characteristics and electroluminescence properties and a valuable strategy for the design of a new generation of blue chromophores with phenothiazine as the donor.