Geminate pair recombination in a conjugated polymer

Upon laser excitation into the S1→S0 transition, delayed luminescence from methyl-substituted ladder-type poly-para-phenylene has been observed. It varies linearly with light intensity, decays according to a power law, IDF∝t−0.8±0.1, and its spectrum consists of an intrinsic and a defect fluorescence band as well as a phosphorescence component. Since the delayed fluorescence part can be quenched by an electric field after excitation, but not the phosphorescence, it must originate from geminate electron–hole recombination rather than from triplet–triplet annihilation.