Charge transport in (formula presented) polymer photovoltaics

Abstract

We study the effect of polymer thickness, hole mobility, and morphology on the device properties of polymer-based photovoltaics consisting of MEH-PPV as the optically active layer, (formula presented) as the exciton dissociation surface, and ITO and Au electrodes. We demonstrate that the conversion efficiency in these polymer-based photovoltaics is primarily limited by the short exciton diffusion length combined with a low carrier mobility. For MEH-PPV devices with optimal device geometry, we achieve quantum efficiencies of 6% at the maximum absorption of the polymer, open circuit voltages of 1.1 V, current densities of 0.4 (formula presented) and rectification ratios greater than (formula presented) under 100 (formula presented) white light illumination. In addition, we achieve fill factors up to 42% at high light intensities and as high as 69% at low light intensities. We conclude by presenting a model that describes charge transport in (formula presented)-based photovoltaics and suggest methods for improving energy conversion efficiencies in polymer-based photovoltaics. © 2001 The American Physical Society.