Highly efficient deep-blue emitting organic light emitting diode based on the multifunctional fluorescent molecule comprising covalently bonded carbazole and anthracene moieties

Abstract

High performance deep-blue organic light-emitting diodes (OLEDs) have been investigated using new multifunctional blue emitting materials 3-(anthracen-9-yl)-9-ethyl-9H-carbazole (AC), 3,6-di(anthracen-9-yl)-9-ethyl-9H-carbazole (DAC), 3-(anthracen-9-yl-)-9-phenyl-9H-carbazole (P-AC), and 3,6-di(anthracen-9-yl)-9-phenyl-9H-carbazole (P-DAC) which comprise covalently bonded carbazole and anthracene moieties. We also have investigated the thermal, electrochemical, and morphological stability to find suitable molecular structure, consisting of carbazole and anthracene moieties. The non-doping deep-blue OLEDs using P-DAC, which showed the highest thermal, electrochemical, and morphological stability, proved the highest luminance efficiency and external quantum efficiency of 3.14 cd A⁻¹ and 2.75%, with the Commission Internationale de l'Eclairage (CIE) chromaticity coordinates (0.162, 0.136) at 100 mA cm⁻². Moreover, the doping devices using P-DAC as the host material showed blue emission, and the high luminance efficiencies and external quantum efficiencies of as high as 7.70 cd A⁻¹ and 4.86% with CIE chromaticity coordinates (0.156, 0.136) and (0.156, 0.217) at 100 mA cm⁻². Both the non-doping and doping devices using P-DAC uniquely exhibited high operational stability with virtually negligible efficiency roll-off over the broad current density range.