Thermal aging of single-layer polymer light-emitting diodes composed of a carbazole and oxadiazole containing copolymer doped with singlet or triplet emitters

An electron-transporting monomer was synthesized that was structurally and energetically similar to the small molecule 2-biphenyl-4-yl-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD). The monomer was copolymerized with 2-(9H-carbazol-9-yl)ethyl 2-methylacrylate and the resulting copolymer was utilized in organic light emitting devices which employed fluorescent coumarin 6 (C6) or phosphorescent tris(2-phenylpyridine)iridium(III) [Ir(ppy)3] emitters. The copolymer devices exhibited a mean luminance of ca. 400 and 3552 cd/m2 with the C6 and Ir(ppy)3 emitters, respectively, that was stable with thermal aging at temperatures ranging from 23 °C to 130 °C. Comparable poly(9-vinyl-9H-carbazole)/tBu-PBD blend devices exhibited more pronounced variations in performance with thermal aging.