Dynamical study on the behavior of electroluminescent polymers under applied electric-fields

The behaviors of the electroluminescent polymers under applied electric fie lds were studied by using the tight-binding model of electron-lattice coupl ing and solving the real-time Newton dynamical equation. It was discovered that (1) the extra electron and hole injected by the applied electric field make the lattice relaxation, and bipolaron-excitons are formed. (2) there exists a critical electric field. When an applied field is equal to or larg er than the critical field, the bipolaron-exciton will be dissociated into positive and negative polarons, leading to photoluminescence quenching. The result is consistent with the relevant experiments, and it also implies th at the bipolaron-exciton is a kind of luminous species in polymers.