have found that by growing semiconductors on a single layer of graphene, the
material transported electric charge better.
The researchers tested
the use of silicon and graphene for the layer, and measured the transport in
those materials in the vertical direction, the direction of charge travel in
organic photovoltaic devices like solar cells or in LEDs.
While they found an
expected difference due to the different crystalline structures and electrical
properties but also discovered something unexpected.
David Barbero of Umeå
University in Sweden, leader of the international research team that performed
the experiments, said that while it was widely believed that a thinner polymer
film should enable electrons to travel faster and more efficiently than a
thicker film, the team discovered that a polymer film about 50 nanometers thick
conducted charge about 50 times better when deposited on graphene than the same
film about 10 nanometers thick.
The team concluded
that the thicker film’s structure, which consists of a mosaic of crystallites
oriented at different angles, likely forms a continuous pathway of
interconnected crystals. This, they theorize, allows for easier charge
transport than in a regular thin film, whose thin, plate-like crystal
structures are oriented parallel to the graphene layer.
By better controlling
the thickness and crystalline structure of the semiconducting film, it may be
possible to design even more efficient graphene-based organic electronic
“The fields most
likely to benefit from this work are probably next-generation photovoltaic
devices and flexible electronic devices,” said Barbero. “Because graphene is
thin, lightweight and flexible, there are a number of potential applications.”