Thesis: Synthesis of Ferroelectric Oxides for photovoltaic applications

PhD defense: Alessandro QUATTROPANI

Title: Synthesis of Ferroelectric Oxides for photovoltaic applications

Team: MaCEPV

Abstract: In this work, we have produced Bi2FeCrO6 oxides (BFCO) by sol-gel technique and pulsed laser deposition (PLD). By sol-gel, precursors in solution were prepared, which are then deposited by centrifugation on silicon or quartz substrates. The numerous structural (XRD) and optical  images (SEM, TEM) analyses carried out on these BFCO films show that the films are fairly homogeneous but exhibit many parasitic phases, which they can be partly eliminated by rapid thermal annealing. Finally, we present the first results obtained on BFCO-SG perovskite devices. On the other hand, BFCO films were deposited on STO and Nb:STO substrates. Their structural, optical and electrical properties are presented. High-quality epitaxial growth and pure-phase films are demonstrated by X-ray diffraction. We show that the band gap of the PLD-BFCO films can be tuned from 1,  9  to  2.6  eV  thanks  to  the  variation  of  growth  conditions.  Theoretical  calculations  has  confirmed  the observed behavior and highlight the importance of the ordering phase. The ferroelectric properties of the PLD films are studied by the piezoresponse force microscopy. Illumination is shown to have a strong effect on polarization. We show that the polarization memory affects the photovoltaic response. Finally, devices based on BFCO are manufactured and their photovoltaic properties are analyzed.

The jury is composed of : Mr. SLAOUI Abdelilah, senior researcher, ICube, CNRS-University of Strasbourg (thesis supervisor), Mr. EL MARSSI Mimoun, Professor, LPMC University of Picardy Jules Verne, Amiens (reviewer), Mrs. BESLAND Marie-Paule, senior researcher (reviewer), Jean Rouxel Materials Institute, Nantes, Mrs. VIART Nathalie, Professor, IPCMS, CNRS-University of Strasbourg (other jury member), Mr. DINIA Aziz, Professor, IPCMS, CNRS-University of Strasbourg (invited member) and Mr. FIX Thomas, researcher, ICube, CNRS-University of Strasbourg (invited member).

The defense will be held in English and will take place on Monday December 17th, 2018, at 9:30 am (IPHC, building 25 of campus Cronenbourg).

Keywords: Oxides, perovskites, ferroelectricity, solar cells, BPVE, BFCO