Optical properties of air-stable semiconducting copolymer based on polythiophene

Optical properties of thiophene based copolymer poly(2,5-bis(3-dodecylthiophen-2-yl)thieno[2,3-b]thiophene) (pBTCT) thin films have been investigated by means of optical absorption, photoluminescene (PL), PL quantum efficiency, time-resolved PL, and electroluminescence measurements. It is found that pBTCT exhibits relatively higher PL quantum efficiency (phi(PL)similar to 16%) in solid state than poly(3-hexylthiophene) (P3HT). Although the PL quantum efficiency is relatively higher, the transition dipole moment of the lowest excited state of pBTCT is not large, as found in P3HT. The electroluminescence from pBTCT light-emitting diodes is observed and its spectrum is essentially the same as the PL spectrum of pBTCT. (C) 2007 American Institute of Physics.