Photovoltaic effect in ferroelectric oxides
ABSTRACT :
In recent years, ferroelectric photovoltaics (FPVs) are being extensively studied due to their anomalously high photovoltages, coupled with switchable photocurrents. The mechanism of ferroelectric solar cell is different from first generation conventional solar cell. In conventional solar cell electron – hole (e - h) pairs are separated by built in potential across the junction, which is an obstacle for the generation of above bandgap photovoltage. On contrary, in ferroelectric system the photogenerated e - h pairs are separated by internal field originated due to the ferroelectric polarization. As a result, high open circuit voltage (VOC) can be even an order of magnitude larger than band gap equivalent voltage of ferroelectric materials. However, FPVs suffer from their extremely low photocurrent, which is due to their wide energy gap between conduction band minima and valence band maxima. Also, the physics behind the generation of above bandgap photovoltage is still in controversy. It is proposed to study the few ferroelectric systems in bulk and films forms for their photovoltaic properties with respect to the bandgap, polarization and electrode geometry which can leads to further insight into the photovoltaic research.