Effects of the Molybdenum Oxide/Metal Anode Interfaces on Inverted Polymer Solar Cells

Inverted polymer solar cells with molybdenum oxide (MoO₃) as an anode buffer layer and different metals (Al or Ag) as anodes are studied. It is found that the inverted cell with a top Ag anode demonstrates enhanced charge collection and higher power conversion efficiency (PCE) compared to the cell with a top Al anode. An 18% increment of PCE is obtained by replacing Al with Ag as the top anode. Further studies show that an interfacial dipole pointing from MoO₃ to Al is formed at MoO₃/Al interfaces due to electron transfer from Al to MoO₃ while this phenomenon cannot be observed at MoO₃/Ag interfaces. It is speculated that the electric field at the MoO₃/Al interface would hinder hole extraction, and hence reduce the short-circuit current.