Synthesis and characterization of topology-varied organic electroluminescent blue-light emitters based on carbazole and triphenylphosphine oxide derivatives

Abstract

Two blue light emitters M-2EtCz and P-2EtCz based on carbazole and triphenylphosphine oxide were synthesized and characterized. The 5% weight loss temperatures of emitters M-2EtCz and P-2EtCz solid powder were 437 and 495 °C, and their photoluminescent quantum yield in solution were 53.93 and 75.78%, which were both significantly improved to those of parent EtCz-Ph. The introduction of triphenylphosphine oxide into EtCz-Ph can lower the lowest unoccupied molecular orbital levels of emitters M-2EtCz and P-2EtCz, while keeping their highest occupied molecular orbital levels unchanged. All the emitters exhibited blue light emission with aggregation-induced enhanced emission characteristic. The non-doped deep blue light-emitting diodes with maximum external quantum efficiencies of 2.68% were obtained for M-2EtCz, and the electroluminescent color purity of P-2EtCz was better than that of M-2EtCz. The doped device hosted by P-2EtCz achieved a maximum brightness of 10,891 cd/m2, external quantum efficiency of 2.04% and current efficiency of 5.65 cd/A.