Highly efficient top-emitting green phosphorescent OLEDs with a narrow band and slow efficiency roll-off for high-definition displays

Abstract

High-definition displays commonly require narrow-band spectra, stability and high efficiency, especially under high brightness. Two ambipolar hosts were developed with xanthone and dibenzofuran as binary n-type units and carbazole as a p-type unit, which showed glass transition temperatures over 140 °C and triplet energies of 2.8 eV. They were used as hosts for tris(2-phenylpyridine)iridium (Ir(ppy)₃) to fabricate top-emission green-phosphorescent organic light-emitting diodes (PhOLEDs). Owing to the strengthened microcavity effect and favorable optoelectronic features of the host materials, the green PhOLEDs exhibited low turn-on voltages of 1.97 and 1.85 V and a narrow full width at half maximum (FWHM) of 28 nm. Furthermore, the maximum current efficiency (CE) and power efficiency (PE) reached as high as 183.1 cd A⁻¹ and 247.3 lm W⁻¹, respectively. More importantly, even at an ultra-high brightness of 66 000 cd m⁻², the efficiencies were maintained at 132.2 cd A⁻¹ and 68.2 lm W⁻¹ and surpassed many similar devices reported previously. In comparison with the prevailing multi-resonance thermally activated delayed-fluorescence (TADF) OLEDs, these top-emitting PhOLEDs were comparable in terms of extremely high efficiency and narrow-band color purity but superior in terms of their exceptional efficiency stability, high brightness, and facile synthesis, all of which make them suitable for practical application in high-definition displays.