Optical and electronic properties of 3,4‐dialkylthiophene‐based p‐/n‐alternating copolymers

Abstract

AbstractFour novel highly soluble p‐/n‐poly[(2,5‐divinyl‐3,4‐dialkylthiophene)‐alt‐2,6‐pyridine] (PA2TV‐Py) and poly[(2,5‐divinyl‐3,4‐dialkylthiophene)‐alt‐(2,5‐diphenyl‐1,3,4‐oxadiazole)] (PA2TV‐OXD) are prepared by Heck coupling approach to compare their photoelectric properties. Characterizations of the copolymers include FT‐IR, 1H‐NMR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), UV–vis spectroscopy, photoluminescence (PL), and electroluminescence (EL). Four alt‐copolymers exhibit excellent solubility in common organic solvents (e.g., CHCl3, THF) and good thermal stabilities, losing less than 5% on heating to ∼ 250°C. The optical properties depict that the band‐gap energy of PA2TV‐Py and PA2TV‐OXD is similarly, ranging from 2.68 to 2.80 eV in solid film and 2.90–2.97 eV in CHCl3 solution. PA2TV‐Pys can emit bright turquoise light with quantum efficiencies (QE) of 30.6 and 53.9%, which about 10‐18 times higher than that of homopolymer in CHCl3 solution. Furthermore, the QE of two PA2TV‐OXDs (purple fluorescence) are increased to 43.6 and 68.5%, respectively, about 1.3–1.4 times higher than that of PA2TV‐Pys. Electrochemical results indicate that the electron affinity (Ea) of four alt‐copolymers range from 2.79 to 3.09 eV, which are propitious to electrons injecting and transporting from the cathode. As a result, these novel copolymers present expected good electroluminescence(EL) performance in their single layer polymer light‐emitting device (PLED) with configuration of ITO/polymer/Al, which turn‐on voltages are between 4.0 and 5.8 V and emit bright green–yellow (538 nm) and yellow (545–552 nm) EL light. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011