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 (TiO
x
) 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
TiO
x
and C70 acceptor fullerene
molecules. We show that defect states in the band gap of TiO
x
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 TiO
x
a
good candidate for the next generation of organic solar cells.
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