Exciton-polaron interaction is one of the major luminescence quenching mechanisms in organic optoelectronic devices. In the first part of our work, we discuss exciton-polaron interaction in pentacene field effect transistors using phase sensitive photocurrent measurements. We investigated the effect of channel charge densities on the photocurrent spectral response and the photocurrent-voltage characteristics. With the help of our steady-state exciton-polaron interaction models, we prove that the observed photocurrent is due to exciton quenching by the injected polarons in the channel. It is observed that for the present system, where charge carrier transport is by hopping, all polarons interact with excitons. This implies that for low mobility systems, the interaction is not limited to deeply trapped polarons.

In the second part of the work, we discuss the interaction between excitons and polarons residing in dissimilar organic materials. This is a common situation in multilayer organic devices. From the gate-modulated steady state photoluminescence quenching measurements in a pentacene/NPB bilayer transistor, we study the quenching of excitons in NPB, by gate induced holes in pentacene. We show that excitons can be quenched by polarons even if they reside in dissimilar molecules, provided that exciton and polaron are separated by a distance within which efficient Forster resonance energy transfer can occur. The experimental findings are supported by a steady-state three dimensional simulation of exciton-polaron quenching efficiency. We estimated the exciton diffusion length of NPB to be in the range of 2.6-3.0 nm and the Forster resonance energy transfer radius to be 2.3-3.0 nm. The proposed device design strategy, to reduce exciton-polaron quenching in organic light-emitting devices, is that the polaron accumulation region must be separated from the location up to which excitons can diffuse efficiently by at least 1.5 times the Forster resonance energy transfer radius.