Geminate pair recombination in a conjugated polymer

Upon laser excitation into the S-1 --> S-0 transition, delayed luminescence from methyl-substituted ladder-type poly-paraphenylene has been observed. It varies linearly with Light intensity, decays according to a power law, I -DF proportional to t(-0.8+/-0.1), and its spectrum consists of an intrinsi c and a defect fluorescence band as well as a phosphorescence component. Si nce the delayed fluorescence part can be quenched by an electric field afte r excitation, but not the phosphorescence, it must originate from geminate electron-hole recombination rather than from triplet-triplet annihilation. (C) 1999 Elsevier Science B.V. All rights reserved.