EFFICIENT PHOTO AND ELECTROLUMINESCENCE OF REGIOREGULAR POLY(ALKYLTHIOPHENE)S

We report absolute photoluminescence (PL) and electroluminescence quan tum efficiencies for thin films and polymer light-emitting diodes prep ared with regioregular (that is, exclusively head-to-head/tail-to-tail conformation and/ or exclusively head-to-tail conformation) poly(alky lthiophenes). In particular, we find a maximum PL quantum efficiency o f similar to 11% for the head-to-head/tail-to-tail conformers, an orde r of magnitude higher than for the head-to-tail conformers. The result s show that chemical conformation plays a crucial role in determining the material electronic structure and, hence, the relevant optical pro perties. The results are significant to the wide field of conjugated, synthetic, light-emitting materials, and hence to the development of l arge-area organic displays. (C) 1998 American Institute of Physics. [S 0021-8979(98)01319-X].