A rigid xanthene–anthracene-based scaffold exhibiting ultra deep blue emission: multifunctional material as emitter and host for blue OLEDs

Abstract

Ultra-deep blue fluorescent emitters with Commission Internationale de L’Eclairage (CIE_y) < 0.08 are still in demand for achieving vibrant full-color displays. Herein, we have synthesized xanthene–anthracene-based 14-(4-(10-phenylanthracen-9-yl)phenyl)-14H-dibenzo[a,j]xanthene (PhAn-Xn), in which xanthene and anthracene are linked by an orthogonal phenyl bridge to prevent aggregation-induced quenching. PhAn-Xn exhibits an emission maximum at 430 nm, with a full width at half maximum (FWHM) of 48 nm, and a prompt lifetime of 0.7 ns. Using neat PhAn-Xn as the emitting material, an organic light-emitting diode (OLED) device was fabricated, achieving a maximum external quantum efficiency (EQE_max) of 4.2%, with CIE coordinates of (0.16, 0.06) at 8 V, following European Broadcasting Union standards, and a maximum luminance (L_max) of 4110 cd m⁻² (at 16.5 V). The device maintains an EQE of 4.0% at 1000 cd m⁻², retaining 95% of its maximum efficiency. PhAn-Xn, which exhibits superior charge transport properties to those of the widely used blue host bis[2-(diphenylphosphino)phenyl]ether oxide, was used as the host material in OLED devices employing the well-known blue dopant 4,4′-bis(9-ethyl-3-carbazovinylene)-1,1′-biphenyl (BCzVBi). The PhAn-Xn-based device exhibits an electroluminescence maximum at 455 nm, consistent with the photoluminescence maximum of BCzVBi. An EQE_max of 6.5% was achieved, along with a maximum brightness of 41 557 cd m⁻² (at 16 V). The device maintains an EQE of 6.4%, retaining 98% of its maximum efficiency at 1000 cd m⁻². These results indicate that PhAn-Xn has multifunctionality and can serve as either an emitter or a host for deep blue OLEDs.