Efficient and bright non-doped blue light-emitting diodes based on glassy styrylcarbazoles

A series of styrylcarbzole fluorophores 9-Ethyl-3-{(E)-2-[4-(1,1,1-triphenylsilyl) phenyl]-1-ethenyl}-9H-carbazole (Cz–SiPh), {4-[2-(9-Ethyl-9H-carbazol-3-yl)-vinyl]-phenyl}-naphthalen-2-yl-phenyl-amine; Cz–NPh and 3-(2-Anthracen-9-yl-vinyl)-9-ethyl- 9H-carbazole (Cz–Ph3) were synthesized via Horner–Emmons–Wadsworth condensation. Fluorophores Cz–SiPh and Cz–NPh emit a blue hue, whereas Cz–Ph3 emits a green hue. Strong emission intensity, stable glassy morphology and blue emission from the solid film make fluorophores Cz–NPh and Cz–SiPh as promising blue emitters. Non-doped organic light emitting devices were fabricated using these fluorophores as an emitting layer directly; 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene and 4,4′-bis(N-naphth-1-yl-N-phenylamino)-biphenyl were used as the electron-transporting layer and the hole-injection layer, respectively. Among these devices, the Cz–NPh-based device exhibits excellent performance, including high brightness (8207 cd/m2), large power efficiency (1.9 cd/A or 1.2 lm/W), high external quantum efficiency (2.3%), high color purity CIE (0.14, 0.09) and good operation stability.