« Ferroelectrics-based photovoltaics »

This project aims to develop ferroelectric materials for photovoltaic applications, in order to create all oxide ferroelectric solar cells without a p-n junction.

Mastering the growth of complex oxides for photovoltaics

The objective of this project is to initiate a novel photovoltaic technology based on inorganic and multifunctional oxides with appropriate bandgap. These oxides are stable, non toxic, abundant and can be processed with a large range of methods and in a large scale (size of the solar cells). The improvement of their performance is possible by adding a degree of multifunctionality. In this project we study an emerging type of solar cells that is based on ferroelectricity. In this type of solar cell, a p-n junction is not always necessary, as opposed to conventional solar cells. They begin to show interesting power efficiencies (up to 8.1 % in 2015), however the mechanisms are not always well understood and there are several challenges to tackle at the material and engineering levels. We mainly focused on the double perovskite Bi₂FeCrO₆ as the photovoltaic absorber. Additional absorbers have been explored, such as BiMnO₃, KBiFe₂O₅ and h-TbMnO₃.

Growth of ferroelectric oxide thin films for the fabrication of devices

The project requires the growth of thin film complex oxides. For this purpose, a pulsed laser deposition system (PLD) was set up thanks to the financial support of ANR. This system enables the growth of thin films at high temperature (up to 950°C), under an oxygen reactive atmosphere, with a base vacuum of 1.5·10^-8 mbar. Furthermore, it allows the use of 4 different targets in one run than can be selected before the deposition. Many targets have been fabricated or purchased within this project.

We first focused on the double perovskite Bi₂FeCrO₆ (BFCO). This was the topic of the PhD of Alessandro Quattropani who defended in December 2018. Films of BFCO were fabricated using the sol-gel technique and pulsed laser deposition. The structural, optical, electrical and surface properties were studied by different techniques, including X-ray resonant diffraction at the ESRF synchrotron. Solar cell architectures were obtained. Other absorbing materials were explored, such as BiMnO₃, KBiFe₂O₅ and h-TbMnO₃.

Main results of the project

We studied many materials as photovoltaic absorbers, mainly Bi₂FeCrO₆ (BFCO), but also BiMnO₃, KBiFe₂O₅ and h-TbMnO₃. In the case of BFCO, epitaxial thin films were obtained without the presence of parasitic phases on SrTiO₃ (001) or Nb-SrTiO₃ (001). The bandgap of BFCO could be varied between 1.9 and 2.6 eV depending on the growth conditions. Solar cells were obtained, with a short-circuit current that is tunable with an applied voltage pulse.

Scientific production

This work has led to 6 publications in international journals with review committee, , in the following journals: Journal of Physical Chemistry C, Solar Energy, Nanoscale, ACS Applied Energy Materials.  Furthermore a book was edited by the coordinator, in which a chapter was written on oxide and ferroelectric solar cells (Elsevier May 2019). In addition the work was presented orally in 5 international conferences or schools including 3 invited ones.

[6] Thickness dependence and strain effects in ferroelectric Bi2FeCrO6 thin films, M. Rastei, F. Gellé, G. Schmerber, A. Quattropani, T. Fix, A. Dinia, A. Slaoui, S. Colis, ACS Appl. Energy Mater. 2, 8550 (2019)
[5] Investigation of KBiFe2O5 as a Photovoltaic Absorber, T. Fix, G. Schmerber, H. Wang, J.-L. Rehspringer, C. Leuvrey, S. Roques, M. Lenertz, D. Muller, H. Wang, A. Slaoui, ACS Appl. Energy Mater 2 (11), 8039-8044 (2019)
[4] Oxide and Ferroelectric Solar Cells, T. Fix, in Advanced micro- and nanomaterials for photovoltaics, Elsevier 2019, ISBN: 978-0-12-814501-2
[3] Tuning photovoltaic response in Bi2FeCrO6 films by ferroelectric poling, A. Quattropani, A. Makhort, M. V. Rastei, G. Versini, G. Schmerber, S. Barre, A. Dinia, A. Slaoui, J.-L. Rehspringer, T. Fix, S. Colis and B. Kundys, Nanoscale 10, 13761 (2018)
[2] Investigation of LaVO3 based compounds as a photovoltaic absorber, M. Jellite, J.-L. Rehspringer, M. A. Fazio, D. Muller, G. Schmerber, G. Ferblantier, S. Colis, A. Dinia, M. Sugiyama, A. Slaoui, D. Cavalcoli, T. Fix, Solar Energy 162, 1 (2018)
[1] Band-gap tuning in ferroelectric Bi2FeCrO6 double perovskite thin films, A. Quattropani, D. Stoeffler, T. Fix, G. Schmerber, M. Lenertz, G. Versini, J. L. Rehspringer, A. Slaoui, A. Dinia and S. Colis, Journal of Physical Chemistry C 122, 1070 (2018)