Synthesis and electroluminescent properties of conjugated copolymer containing phenothiazine and phenanthridine unit

Abstract

Conjugated copolymer, poly[N-(2-ethylhexyl)phenothiazine-alt-6-phenyl phenanthridine] [poly(PZ-PTI)], with azomethine linkage was synthesized by Schiff-base reaction. This new conjugated copolymer exhibited improved solubility in common organic solvents due to the presence of alkyl side chains on phenothiazine rings as well as polar azomethine groups in main chains. Single-layered PLED made with poly(PZ-PTI) as an emitting layer exhibited EL (emission) at 572 nm (yellow; color coordinates of x = 0.51, y = 0.48). Double-layered PLED fabricated with the synthesized polymer as an emitting layer and Alq3 as an electron transporting layer exhibited enhanced EL emission and efficiency compared to that of single-layered PLED. With increasing the thickness of Alq3 layer in double-layered PLED the emission peak gradually shifted to the single-layered PLED made with only Alq3 as an emitting layer, confirming good hole transporting behaviour of the synthesized conjugated copolymer.