Deciphering Electron Interplay At The Fullerene/Sputtered Tiox Interface: A Barrier-Free Electron Extraction For Organic Solar Cells

Organic photovoltaics (OPVs) technology now offers power conversion efficiency (PCE) of over 18% and is one of the main emerging photovoltaic technologies. In such devices, titanium dioxide (TiOx) has been vastly used as an electron extraction layer, typically showing unwanted charge-extraction barriers and the need for light-soaking. In the present work, using advanced photoemission spectroscopies, we investigate the electronic interplay at the interface between low-temperatures-puttered TiOx and C-70 acceptor fullerene molecules. We show that defect states in the band gap of TiOx are quenched by C-70 while an interfacial state appears. This new interfacial state is expected to support the favorable energy band alignment observed, showing a perfect match of transport levels, and thus barrier-free extraction of charges, making low-temperature-sputtered TiOx a good candidate for the next generation of organic solar cells.