Loss processes in organic double-heterostructure laser diodes

Abstract

At high current densities, the characteristics of organic laser diode structures are strongly influenced by a variety of loss processes such as bimolecular annihilations, field-induced exciton dissociation and induced absorptions due to polarons and triplet excitons. Here, we investigate a TE₂-mode organic double-heterostructure laser diode by numerical simulation. The electrical properties are described using a numerical drift-difusion model and the optical characteristics are modeled using a transfer matrix method. When annihilation processes are included, a threshold current density of 8.5 kA/cm² is derived for the considered device. Laser operation is not achieved when field-induced exciton dissociation is considered. For induced absorptions, maximum relative cross sections of 9.6 × 10^-8 for polarons and 1.4 × 10^-4 for triplet excitons have been calculated, which would still allow laser operation. For higher relative absorption cross sections, laser operation is suppressed for all current densities. Furthermore, the impact of field quenching is analyzed and the separation of singlet excitons from polarons and triplet excitons in the time domain is studied.