We report a novel interconnecting layer (ICL) consisting of MoO3/Au/Al/ZnO for efficient operation of inverted homo-tandem organic solar cells employing poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C61-butyric acid methyl ester (PCBM). It was found that the ultrathin metal bilayer of Au/Al, a few nanometers, can align the energy levels and play a significant role in the charge extraction and recombination within the ICL. And the ICL showed an electrically ohmic-contact, high transmittance and very planar morphology for tandem application. The performance of air-fabricated homo-tandem organic solar cells with this new ICL delivered an average power conversion efficiency (PCE) of 3.0%, which is very close to the PCE of 3.3% from the state-of-the-art P3HT:PCBM based homo-tandem organic solar cells. Meanwhile, thermal stability tests at an elevated temperature of 150 degrees C for 12 h showed stable ICL with successful operation. (C) 2017 Elsevier Ltd. All rights reserved.