Excitons in electroluminescent polymers: poly(para-phenylene), poly(para-phenylenevinylene) and poly(para-phenylenedivinylene)

We study photoexcited states with large exciton radius in electroluminescent polymers, poly(para-phenylene) (PPP), poly(para-phenylenevinylene) (PPV) and poly(para-phenylenedivinylene) (PPD), by the intermediate exciton theory. We compare properties of excitons in these three polymers. The oscillator strengths of the long-range excitons in PPP are smaller than in PPV, and those of PPD are larger than in PPV. Such relative variations are explained by the differences in the number of vinylene bonds.