Exciton separation at the interface between pentacene and dipolar chromophore

We demonstrate photo-induced charge transfer between pentacene and dipolar chromophore, disperse red 19 (DR19), which can be applied in fabricating optoelectronic devices with abundant flexibility due to the functionality of the dipolar chromophore at the interface. Photo-induced charge transfer phenomenon between pentacene and DR19 is explored through pentacene thickness-dependent threshold voltage measurements using pentacene/DR19 bilayer field effect transistors under illumination. Threshold voltage increases as pentacene thickness increases up to a certain thickness followed by a decrease, resulting in a peak threshold voltage. The presence of the peak explains competition between optical absorption in the pentacene layer and exciton diffusion followed by exciton separation at the pentacene/DR19 interface. The exciton diffusion length in pentacene is estimated using an exciton diffusion-dissociation model.