Novel 9,9-dimethylfluorene-bridged D–π–A-type fluorophores with a hybridized local and charge-transfer excited state for deep-blue electroluminescence with CIEy ∼ 0.05

Abstract

Deep-blue light emitting materials are of great significance in the fields of commercial full-color organic light-emitting diodes (OLEDs) and solid-state lighting. The hybridized local and charge-transfer excited state (HLCT) is a promising strategy to achieve deep-blue emission and high photoluminescence quantum yield. Based on HLCT, we designed and synthesized two novel donor–π–acceptor, 9,9-dimethylfluorene-bridged fluorophores (DFPBI & TFPBI) for efficient deep-blue OLED applications. Non-doped devices, with DFPBI and TFPBI as emitters, exhibit deep-blue emission with CIE coordinates of (0.154,0.042) and (0.152,0.054), accompanied by good EL performance with maximum external quantum efficiencies (EQEs) of 4.18% and 5.74%, respectively. In particular, the TFPBI-based non-doped device displays a slow efficiency roll-off at high luminance with an EQE of 5.50% and 4.80% at 100 cd m⁻² and 1000 cd m⁻², respectively. This work not only demonstrates the potential of these two fluorophores in deep-blue OLEDs, but also provides tactics for the design of deep-blue light emitting materials by using the 9,9-dimethylfluorene-bridged D–π–A architecture.