Increased efficiency of small molecule photovoltaic cells by insertion of a MoO3 hole-extracting layer

Abstract

We report a ∼60% increase in open circuit voltage (V_oc) and power conversion efficiency in a chloroaluminium phthalocyanine (ClAlPc)/fullerene (C₆₀) planar heterojunction photovoltaic device after insertion of a MoO₃ hole-extracting layer at the interface between the indium tin oxide (ITO) electrode and the ClAlPc donor layer, with an associated improvement in device stability. A similar improvement was observed in heterojunction devices based on mixed ClAlPc/C₆₀ layers. We propose that the improvements in device performance are due to the pinning of the ITO Fermi level to the valance band of the MoO₃ interlayer, where the latter is closely aligned with the highest occupied molecular orbital of ClAlPc.