DS0201 -

Ferroelectrics based photovoltaics – FERROPV

Photovoltaics based on ferroelectric materials

We propose to study an emerging type of solar cell based on ferroelectricity. In this type of solar cell, a p-n junction is not a prerequisite, as opposed to conventional solar cells. Interesting conversion efficiencies start to be obtained with such a technlogoy (up to 8.1% in 2015), however mechanisms are not well understood and there are several challenges at the material science and engineering levels.

Master the growth of complex oxides for photovoltaics

Inorganic thin film photovoltaics (PV) are mainly based on CdTe, amorphous Si or CIGS. The ideal bandgap of an active photovoltaic layer for the solar spectrum is around 1.3 eV. However oxides with low bandgaps are scarce. One of the most studied oxides as an active photovoltaic layer to date is cuprous oxide, Cu2O. Its bandgap is around 2.1 eV and so it is not ideal for the solar spectrum. Its conversion efficiencies do not generally exceed 4%. In the most recent times, hybrid organo-metal halide perovskites have emerged with the highest conversion efficiencies reported of more than 20 %. However, these materials present stability, reliability, scalability and toxicity problems. Of course, research in this area is focusing hard on these challenges, but success is not guaranteed. Alternative inorganic oxides could offer significant advantages. The objective of this project is to initiate a game-changing photovoltaic technology based on new multifunctional inorganic oxide materials with suitably low bandgaps. These oxides are stable, non-toxic, abundant and processable by a range of scalable methods. Radically enhanced performance is certainly possible through incorporating multifunctionality into them.

We aim to synthetize ferroelectric materials that absorb a large part of the solar spectrum with reduced bandgap width. We explore several promising materials: BiMnO3, Bi2FeCrO6, KBiFe2O6 and TbMnO3. Doping of Bi2FeCrO6 is envisaged. For these materials, the project consists in the thin film growth and evaluation of the structural, optical and electrical properties in order to better understand these materials. Then, the most promising materials are integrated into all oxide solar cells and their potential for photovoltaics is evaluated.

We released three publications on oxide for photovoltaics. An invited talk will be delivered at the Materials Research Society (MRS) conference end of November 2018. We particulary focused on Bi2FeCrO6 that is a promising double perovskite. We deposited it by pulsed laser deposition epitaxially on SrTiO3 (001) and Nb-SrTiO3 (001). We demonstrated that it is possible to adjust the bandgap of these films from 2.6 to 1.9 eV, by modifying the repetition rate of the laser. A low repetition rate induces a better Fe/Cr ordering in the double perovskite, reducing the bandap of the material. This picture is confirmed by ab ignition band structure calculations that demonstrate that the presence of antisite defects leads to an increase of the bandgap of 0.25 eV compared to the ideal structure. In terms of devices, we showed that the photovoltaic effect provides a hysteresis as a function of the electric field applied initially and the poling history of the sample. We demonstrated as well that light can depolarize electrically the films which was observed by PFM (piezoresponse force microscopy). Work on two additional materials, KBiFe2O5 and TbMnO3, is still ongoing and efforts are undertaken to obtain the right phases.

A pulsed laser deposition system was installed as part of this ANR project in order to grow oxide thin films. Three publications have been realized during the period, on oxides for photovoltaics. A book is being published by Elsevier, based on advanced materials and concepts for photovoltaics. We obtained a Bi2FeCrO6 solar cell whose properties can be controlled with an initial voltage pulse, but its conversion efficiency still needs to be improved. Synchrotron measurements have been realized at ESRF in order to evaluate the Fe/Cr order ration in Bi2FeCrO6 with different bandgaps.

-[submitted] Thickness dependence and strain effects in ferroelectric Bi2FeCrO6 thin films, M. V. Rastei, F. Gellé, G. Schmerber, A. Quattropani, T. Fix, A. Dinia, A. Slaoui, and S. Colis
-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 Applied Energy Materials, accepted
-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)
-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)
-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)

In addition, five oral communications in international conferences were presented including three invited ones, and one communication in a national conference.
Also, a book was edited by the coordinator:
Book editor: Advanced micro- and nanomaterials for photovoltaics, edited by D. Ginley and T. Fix, Elsevier 2019, ISBN: 978-0-12-814501-2
Oxide and Ferroelectric Solar Cells, T. Fix, in Advanced micro- and nanomaterials for photovoltaics, Elsevier 2019, ISBN: 978-0-12-814501-2

Inorganic thin film photovoltaics (PV) are mainly based on CdTe, amorphous Si or CIGS. In the most recent times, hybrid organo-metal halide perovskites have emerged with the highest conversion efficiencies reported of 20.1 %. However, these materials present stability, reliability, scalability and toxicity problems. Of course, research in this area is focusing hard on these challenges, but success is not guaranteed. Alternative inorganic oxides could offer significant advantages.

The ideal bandgap of an active photovoltaic layer for the solar spectrum is around 1.3 eV. However oxides with low bandgaps are scarce. One of the most studied oxides as an active photovoltaic layer to date is cuprous oxide, Cu2O. Its bandgap is around 2.1 eV and so it is not ideal for the solar spectrum. Its conversion efficiencies do not generally exceed 4%.

In this project we propose to study an emerging type of solar cells that is based on ferroelectricity. In this type of solar cell, a p-n junction is not necessarily needed, as opposed to conventional cells. Interesting efficiencies start to be obtained with this type of solar cells (up to 8.1 %, in 2015), yet the mechanisms are still not well understood and there are several materials and engineering issues to be tackled.

The objective of this project is to initiate a game-changing photovoltaic technology based on new multifunctional inorganic oxide materials with suitably low bandgaps. These oxides are stable, non-toxic, abundant and processable by a range of scalable methods. Radically enhanced performance is certainly possible through incorporating multifunctionality into them. There are five highly structured WPs in this project which when put together will ensure the greatest chance of success.

We aim to synthetize ferroelectric materials that absorb a large part of the solar spectrum and have reduced bandgaps. We will explore four types of materials with promising properties: BiMnO3, doped BiFeO3, Bi2FeCrO6, and doped TbMnO3. For these materials, the project will consist in growing thin films and assess their structural, optical and electrical properties to better understand these materials. Then, the most promising materials will be integrated into all oxide solar cells and their potential for photovoltaics will be evaluated.

Project coordination

Thomas FIX (Laboratoire des sciences de l'ingénieur de l'informatique et de l'imagerie)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

ICube Laboratoire des sciences de l'ingénieur de l'informatique et de l'imagerie

Help of the ANR 115,560 euros
Beginning and duration of the scientific project: September 2016 - 36 Months

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