Windmill-type molecules for efficient deep-blue organic light-emitting diodes via hybridized local and charge-transfer excited state

Abstract

Twisted bipolar molecules with hybridized local and charge-transfer (HLCT) excited states have been demonstrated to form an efficient strategy for achieving high-performance deep-blue electroluminescence (EL) by harvesting both singlet and triplet excitons. In this study, two windmill-type molecules featured with HLCT excited state characteristics were synthesized and they exhibited excellent thermal, morphological and photophysical properties and electrochemical stabilities. Excellent deep-blue EL performances were achieved using 2C2P as an emitter with maximum luminance, current efficiency, power efficiency and external quantum efficiency of 2698 cd m⁻², 3.5 cd A⁻¹, 3.3 lm W⁻¹ and 7.6%, respectively. Excellent color purity was found with an emission maximum of 418 nm, Commission Internationale de l’Eclairage coordinates of (0.162, 0.066) and a small full width at half maximum of 55 nm. The results indicate that excellent deep-blue EL performances can be achieved with typical donor–acceptor molecules exhibiting the HLCT process and a large horizontal dipole ratio.