Asymmetric deep-blue tetrafluorobenzene-bridged fluorophores with hybridized local and charge-transfer characteristics for efficient OLEDs with low efficiency roll-off†

Abstract

High dynamic range technology places greater demands on organic light-emitting diode (OLED) displays, particularly blue emitters, which face significant challenges in meeting the wide-color-gamut BT.2100 standard and achieving high efficiency at high brightness. Here, we propose a design strategy for constructing bipolar deep-blue materials by combining an asymmetric donor–acceptor–donor′ (D–A–D′) type structure with a novel tetrafluorobenzene acceptor. The resulting molecules feature typical hybridized local and charge-transfer state characteristics, with high oscillator strengths, achieving high fluorescence efficiencies exceeding 80% and fast radiative rates that surpass 6 × 10⁸ s⁻¹. Consequently, the doped device emits a deep-blue light with color coordinates of (0.159, 0.048), and demonstrates a maximum external quantum efficiency (EQE) of 6.35%, maintaining efficiencies of 5.95% and 5.61% at 500 and 1000 cd m⁻², respectively. Remarkably, the non-doped OLED boasts a superior EQE of 7.44%, retaining an impressive 6.99% even at 1000 cd m⁻² and maintaining a high 6.19% up to a brightness of 10 000 cd m⁻², demonstrating minimal efficiency roll-off. These findings underscore the great potential of the tetrafluorobenzene-based D–A–D′ type molecular design strategy in developing efficient blue materials and their optoelectronic applications.