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.