7th International Congress on Ceramics

Effect of polarization, domain structure and interfaces on the photovoltaic properties of ferroelectric thin films

Reference	Presenter	Authors (Institution)	Abstract
08-122	José Antônio Eiras	Gonçalves, A.M.(Universidade Federal de São Carlos); Eiras, J.A.(Universidade Federal de São Carlos);	The photovoltaic effect in ferroelectric materials has gained much attention recently. The use of this property adds more functionality to these materials and, on the other side, it is expected that with them higher efficiencies can be achieved. Understanding the mechanisms of photogeneration and transport in ferroelectrics is a key topic in materials science and solid-state physics. In this work, the photovoltaic effect in ferroelectric thin films was investigated considering a macro and microscopic analysis of ferroelectric properties. Pb(Zr0.2,Ti0.8)O3 (PZT) and Pb(Fe0.5,Nb0.5)O3 (PFN) thin films were grown on polycrystalline ITO/Glass substrates by rf sputtering. XRD showed that PZT films are tetragonal with c/a factor of 1.034, while PFN is pseudocubic. The permittivity dependence on electric field ( $ε$ -E) was measured and the curves were fitted with a phenomenological model, that considers the ferroelectric domain structure [1]. We found a “slim-loop” response for PFN films with a strong decrease of $ε$ with the applied field, and a more classical “square” response for PZT films. Maximum relative permittivity of 167 and 426 and a coercive field of 211 and 80 kV/cm were found for PZT and PFN respectively. Hysteresis loop were reconstructed from the fittings. We found similar saturation polarization for PZT and PFN, while the remnant polarization was two orders of magnitude lower for PFN. The short circuit current (Isc, V=0) under illumination with white light, after applying different poling voltages, showed a strong hysteretic behavior for PZT, with coercive field similar to the obtained from the $ε$ xE curves, and a modulation of 225% of the Isc, while a smaller change was observed for PFN films, i.e., 30%, evidencing the strong influence of the polarization on the photovoltaic response. Finally, the relative efficiency was higher for PZT than for PFN films. [1] Placeres-Jiménez, R. et al., J. Phys. D: Appl. Phys. 48, 465301 (2015)
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