Polarization dependent ferroelectric photovoltaic effects in BFTO/CuO thin films

Bi5FeTi3O15 (BFTO) and BFTO/CuO films were deposited by a sol-gel technique, which exhibited macroscopic ferroelectric properties. It was found that the BFTO/CuO films showed a short circuit photocurrent density (Jsc) enhanced by nearly 10 times and power conversion efficiency increased by 13-fold compared to those of the BFTO film. The significant increase in the photovoltaic (PV) response may be attributed to the p-n junction internal electric field acting as the driving force of photogenerated carriers. Furthermore, both BFTO and BFTO/CuO films indicated a switchable PV response in both polarities. The open circuit voltage (Voc) and Jsc for BFTO and BFTO/CuO were observed to be −0.59 V and +43.88 μA/cm2 and −0.23 V and +123.16 μA/cm2, respectively, after upward poling, whereas after downward poling, +0.11 V and −6.26 μA/cm2 and +0.17 V and −83.21 μA/cm2 for BFTO and BFTO/CuO were observed, respectively. The switchable PV responses were explained by the ferroelectric depolarization field, whose directio...