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 (CIEy) < 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), where 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 maxima (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 (EQEmax) of 4.2%, with CIE coordinates of (0.16, 0.06) at 8 V, following European Broadcasting Union standards and a maximum luminance (Lmax) 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, exhibiting superior charge transport properties compared to the widely used blue host, namely bis[2-(diphenylphosphino)phenyl]ether oxide, was employed as the host material in OLED devices employing well-known blue dopant 4,4’-bis(9-ethyl-3-carbazovinylene)-1,1’-biphenyl (BCzVBi). The PhAn-Xn-based doped device exhibits electroluminescence maximum at 455 nm, consistent with the photoluminescence maximum of BCzVBi. An EQEmax of 6.5% was achieved, along with a maximum brightness of 41557 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 host for deep blue OLEDs.