Simultaneous enhancement of charge transport and exciton diffusion in poly(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi></mml:math>-phenylene vinylene) derivatives

Abstract

Time-resolved luminescence spectroscopy has been used to investigate exciton diffusion in thin films of poly($p$-phenylene vinylene) (PPV)--based derivatives. Due to chemical modifications the PPV derivatives differ by three orders of magnitude in charge carrier mobility as a result of a reduced energetic disorder. From the photoluminescence decay curves of PPV/fullerene heterostructures, the exciton diffusion coefficient was found to increase by one order of magnitude with decreasing disorder. This increase in the diffusion coefficient is compensated by a decrease of the exciton lifetime, leading to an exciton diffusion length of $5--6\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ for the various PPV derivatives.