Enhanced ferroelectric photovoltaic effect based on converging depolarization field

• Effects of tubular radius on the photovoltaic effects have been investigated.
• The photovoltaic effect can be enhanced by increasing the tubular radius.
• The short circuit current is as large as 0.31 mA/cm2.
• The power conversion efficiency is as high as 0.82%.
• The efficiency is about 250- fold of magnitude larger than that of other results.

We report a photovoltaic effect in ferroelectric Bi0.9La0.1FeO3 ferroelectric films grown on SrTiO3 substrates with tubular La0.7Sr0.3MnO3 films as buffer layers. The photovoltaic effect can be enhanced by increasing the tubular radius of La0.7Sr0.3MnO3 bottom electrode, the open circuit voltage, short circuit current and power conversion efficiency are 2.05 V, 0.31 mA/cm2 and 0.82%, respectively. Remarkably, the efficiency is about 250- fold of magnitude larger than that of ordinary sandwich structure for visible wavelengths. The role of converging electric field formed by asymmetric top and bottom electrodes is similar to that of an electrostatic lens, and it is suggested to be the reason of such significant photovoltaic effect. Our results imply that the conversion efficiency of ferroelectric photovoltaic can be strengthen effectively by converging electric field, suggesting that the photovoltaic effect in ferroelectric thin films could be further explored for solar light photovoltaic applications.

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