Indium tin oxide-free inverted polymer solar cells with ultrathin metal transparent electrodes

Efficient indium tin oxide (ITO)-free inverted polymer solar cells (PSCs) were fabricated by applying ultrathin metal transparent electrodes as sunlight incident electrodes. Smooth and continuous Ag film of 4 nm thickness was developed through the introduction of a 2 nm Au seed layer. Ultrathin Ag transparent electrode with an average transmittance of up to 80% from 480 to 680 nm and a sheet resistance of 35.4 Ω/sq was obtained through the introduction of a ZnO anti-reflective layer. The ultrathin metal electrode could be directly used as cathode in polymer solar cells without oxygen plasma treatment. ITO-free inverted PSCs obtained a power conversion efficiency (PCE) of 5.2% by utilizing the ultrathin metal transparent electrodes. These results demonstrated a simple method of fabricating ITO-free inverted PSCs. © 2017, Higher Education Press and Springer-Verlag GmbH Germany.