PPV based polymer light-emitting diodes: interface modeling and energy band diagram

Summary form only given. We investigate the energy band diagrams and electric field distributions of polymer light emitting diodes under low injection conditions. The metal is modeled by a fixed chemical potential whereas the polymer is described by the Brazovskii-Kirova continuum model. We consider bias conditions for which there is a depleted region in the center of the device. The two contact regions, which are separated by the depletion region, are each considered to be in thermal equilibrium. However, equilibrium is not established between the separated contacts. We calculate the distribution of excitations as a function of position, bias potential and the confinement parameter. Injected or photogenerated carriers form a bipolaron lattice in the vicinity of the interface with bipolaron density decreasing progressively away from the interface. At a characteristic penetration length the bipolaron density goes to zero. In addition, we calculate the total charge and capacitance of the contact area as a function of the confinement parameter. The results are interpreted in view of capacitance measurements as a function of voltage and frequency.