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-temperature-sputtered TiOx and C70 acceptor fullerene molecules. We show that defect states in the band gap of TiOx are quenched by C70 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.
Bibliografisk noteFunding Information:
We are grateful to ALOISA beamline staff for providing support and assistance during the beamtime. We acknowledge the financial support from ALOISA synchrotron facility. M.M. acknowledges Danmarks Frie Forskningsfond, DFF FTP for funding of the project React-PV, No. 8022-00389B and the support from the project SMART—Structure of MAterials in Real Time, funded by the Danish Ministry of Higher Education and Science. The research leading to this result has been supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Program for Research and Innovation HORIZON 2020.
© 2021 American Chemical Society.