Abstract
We report absolute photoluminescence (PL) and electroluminescence quantum efficiencies for thin films and polymer light-emitting diodes prepared with regioregular (that is, exclusively head-to-head/tail-to-tail conformation and/ or exclusively head-to-tail conformation) poly(alkylthiophenes). In particular, we find a maximum PL quantum efficiency of similar to 11% for the head-to-head/tail-to-tail conformers, an order of magnitude higher than for the head-to-tail conformers. The results show that chemical conformation plays a crucial role in determining the material electronic structure and, hence, the relevant optical properties. The results are significant to the wide field of conjugated, synthetic, light-emitting materials, and hence to the development of large-area organic displays. (C) 1998 American Institute of Physics. [S0021-8979(98)01319-X].