The sun seems to be our only truly dependable source of renewable energy, and scientists are constantly on the hunt for innovative ways to convert sunlight into electricity. The potential of thin ferroelectric films for visible-light photovoltaic devices has now been demonstrated by researchers from the A*STAR Institute of Materials Research and Engineering and the National University of Singapore.
Photovoltaic devices, including solar cells, produce electricity when the absorption of light provides electrons with enough energy to cross a barrier called the bandgap. To generate a useful electrical current, however, these charge carriers must be swept along in a particular direction rather than flowing randomly. In the most commonly used photovoltaic materials, such as silicon, scientists achieve this by constructing a device with a material interface referred to as a p–n junction.
Alternatively, scientists can exploit the ‘bulk photovoltaic effect’ of ferroelectric materials, by which photocurrent can flow in a uniform material without the need to form an interface. “In ferroelectric materials, the photovoltage magnitude is not limited by an energy barrier like it is in semiconductor photovoltaic materials,” explains senior A*STAR scientist Kui Yao. “The reason is that the underlying mechanism is fundamentally different.” Yao and his co-workers identified and studied bulk photovoltaic phenomena in a thin film made of bismuth ferrite (BFO).
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