Synthesis and Characterization of a New p-n Diblock Light-Emitting Copolymer.

In this paper we present the synthesis and characterization of a new light-emitting copolymer constituted of regularly alternating segments of 3,3'-didecyl-2,2'-bithiophene and 2,6-bis(1,3,4-oxadiazolyl)toluene, which are p-dopable and n-dopable, respectively. The new polymer emits intense green light under the irradiation of UV light in its film states and shows strong solvatochromism both on absorption and on emission. The n-doping potential of the polymer is measured to be similar with that of 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) and other reported oxadiazole-containing polymers, the currently excellent electron-transporting materials, while its p-doping potential is much lower than those of other oxadiazole-containing light-emitting polymers and is comparable with that of poly(p-phenylenevinylene) (PPV) and polythiophenes (PT), the typical p-dope type materials. The presented synthesis reveals a possible approach to balance the rates of injection of electrons and holes from opposite contacts into an emissive layer in polymer light-emitting diodes by controlling the intrinsic properties of light-emitting materials.