B. Xu et al., NONRADIATIVE DECAY CHANNELS IN POLY(3-HEXYLTHIOPHENE) AND POLY(3-DODECYLTHIOPHENE) AND HOW TO CONTROL THEM BY MOLECULAR ENGINEERING, Thin solid films, 243(1-2), 1994, pp. 638-642
We report a photoluminescence study of poly(3-alkylthiophene) films. T
he quantum yield of photoluminescence of amorphous films is higher tha
n that of semicrystalline films. Temperature dependence measurements r
eveal an intrachain non-radiative decay channel (NRDC) with an activat
ion energy of 0.015 eV in semicrystalline films. The quantum yield inc
reases with increasing alkyl chain length, suggesting that an intercha
in NRDC is also responsible for the low quantum yields in these materi
als. We find that the confinement parameter gamma of the polaron-excit
on increases when the film order increases, indicating that the two su
blevels are closer to the band edge in ordered films owing to a strong
intermolecular interaction. The value of gamma for poly(3-dodecylthio
phene) is lower than that for poly(3-hexylthiophene), indicating a lar
ger tight-binding energy in the former.