Merocyanine organic solar cells

Abstract

Recently, we reported on the development of a new thin‐film organic solar cell with an AM1 sunlight efficiency of about 0.7% for large area devices (∼1 cm²). This relatively high‐efficiency MIS‐Schottky barrier‐type cell was based on merocyanine type photosensitizing dyes. In this paper we present additional experimental results and develop a comprehensive theoretical model to explain the observed photovoltaic properties. The model incorporates the generation, transport, and surface dissociation of excitons and field‐dependent quantum efficiency. The low fill factor of 0.3 was attributed mainly to the field dependence of quantum efficiency. An exciton diffusion length of 60 Å was determined by analyzing the short‐circuit photocurrent action spectra using the theoretical model developed. The diffusion potentials for metal/merocyanine Schottky barrier cells for six different metals were determined by C‐V measurements; the diffusion potential increases with decreasing work function. As solar cells, these devices have higher efficiencies when there is a very thin interfacial oxide layer between the barrier forming metal and merocyanine.