Dissociation of excitons in organic light-emitting diodes

In this paper, the dissociation of excitons in both doped and undoped organic light-emitting diodes is investigated in detail by means of electric-field-induced photoluminescence quenching. The results show that the doped devices demonstrate lower quenching than that of undoped device. The reason is that the narrower energy band gap of guest molecules compared to that of the host molecules. In doped devices the increasing concentration of the guest molecules leads to a decrease in dissociation of excitons. The reason is that the increasing of the guest molecules concentration can result in an increase in the fraction of excitons residing on the guest molecules. Besides, the decreasing energy band gap of guest molecules can also make lower quenching in the doped devices.