Mathilde Fievez

Research Interests

Fig. 1: Monitoring the degradation of RSPP devices using automated optical imaging combined with manual J-V monitoring. Understanding the effects of modified processing parameters and device structure on the kinetics and mechanisms of degradation is crucial to take perovskite solar cells closer to commercialization. Research efforts focus on both the initial perovskite precursor ink, which can contain pre-formed clusters that affects crystallization, and on the final films whose morphology influence device performance and stability.

Photovoltaic devices based on metal halide perovskite photoactive layers have gained interest at both research and industrial scale thanks to their lower environmental footprint (energy payback time ~ months), state-of-the-art power conversion performances (over 25%) and compatibility with high throughput fabrication processes (~ 1m2/min). My research aims at developing scalable deposition processes to deposit the perovskite layer over large-area substrates. The main challenge lies in controlling the crystallization of perovskite crystals from a precursor ink into a compact, crystalline, and homogeneous films at both micro- and macroscopic scales.
The combination of substrate heating and gas quenching is a successful approach to control the crystallization of slot-die coated wet precursor films. In such a system, I have studied how the precursor ink formulation (perovskite composition, solvents, additives…), the processing parameters and the device structure employed impact the resulting photovoltaic performances. In particular, understanding the correlation between perovskite material properties and device performance is crucial to choose the most relevant device architecture. Today, my research focuses on another technology - perovskite spray-coating with plasma-assisted crystallization- with the aim to study this innovative crystallization strategy to fabricate large-area perovskite solar modules with high efficiency and good durability.

Fig. 2: From the control of the perovskite crystallization to the fabrication of large-area photovoltaic devices. (collaboration CEA INES-NTU)

A key challenge for industrialization of this technology is to homogeneously solution-process the perovskite layer over large-area substrates. In this case, both the wet film formation process (spray-coating or slot-die coating) and the curing medium (plasma or gas quenching) can induce perovskite film thickness variations. Those variations are detrimental to the performances of large-area photovoltaic modules and needs to be assessed carefully during the fabrication. To non-destructively assess the quality of perovskite thin film deposited on glass substrate, we developed a quantification method based on white light images and machine vision algorithms to extract metrics relevant to researchers during process development. This method was developed in collaboration between CEA INES and Pr. Berlinguette group in university of British Columbia.

Fig. 3: A machine vision tool to quantify the perovskite layer quality over large-area substrates. (collaboration CEA INES-UBC)

Publications

First author contributions (*Equal contributions):

• N. Taherimakhsousi*, M. Fievez*, B.P. MacLeod*, E.P. Booker, E. Fayard, M. Matheron, M. Manceau, S. Cros, S. Berson, C.P. Berlinguette, "A machine vision tool for facilitating the optimization of large-area perovskite photovoltaics | npj Computational Materials" (nature.com) ​​​, npj Computational Materials, volume 7, Article number: 190 (2021) 
• M. Fievez*, P.J.S. Rana, T.M. Koh, M. Manceau, J.H. Lew, N.F. Jamaludin, B. Ghosh, A. Bruno, S. Cros, S. Berson, S.G. Mhaisalkar, W.L. Leong, “Slot-die coated methylammonium-free perovskite solar cells with 18% efficiency”, Solar Energy Materials and solar cells, 2021, DOI: 10.1016/j.solmat.2021.111189
• Contributing author publications:
• K.K. Sears, M. Fievez, M. Gao, H.C. Weerasinghe, C.D. Easton, D. Vak, “ITO-Free Flexible Perovskite Solar Cells Based on Roll-to-Roll Slot-Die Coated Silver Nanowire Electrodes”, Solar RRL, 2017, DOI: 10.1002/solr.201700059

Conference Proceedings and Presentations

• M.Fievez, E. Fayard, C. Roux, W.L. Leong, M. Manceau, S. Cros, S. Berson, W.L. Leong, Tuning precursors stoichiometry fot high efficiency scalable perovskite photovoltaics, EUPVSEC, online, September 2021, Oral presentation.
• M.Fievez, E. Fayard, C. Roux, W.L. Leong, M. Manceau, S. Cros, S. Berson, “Tuning Precursors Ink Stoichiometry for High Efficiency Scalable Perovskite PV”, IEEE, online, June 2021

Oral Presentations

• M. Fievez, P.J.S. Rana, T.M. Koh, M. Manceau, E. Fayard, M. Matheron, S. Cros, S. Berson, A. Bruno, S. Mhaisalkar, W.L. Leong, N. Taherimakhsousi, B.P. MacLeod, E.P. Booker, C.P. Berlinguette, Gas assisted Crystallization of MA free Slot die coated perovskite films towards module fabrication, JNPV, online, January 2021 – Invited oral presentation
• M. Fievez, P.J.S. Rana, T.M. Koh, M. Manceau, J.H. Lew, N.F. Jamaludin, B. Ghosh, A. Bruno, S. Cros, S. Berson, S.G. Mhaisalkar, W.L. Leong, “Slot-die coating of double cation perovskite: from ink tuning to high efficiency devices”, EUPVSEC, Marseille, France, September 2019 – Oral presentation
• M. Fievez, P.J.S. Rana, T.M. Koh, M. Manceau, J.H. Lew, N.F. Jamaludin, B. Ghosh, A. Bruno, S. Cros, S. Berson, S.G. Mhaisalkar, W.L. Leong, “Slot-die coating of double cation perovskite: from ink tuning to high efficiency devices”, ICMAT, Singapore, June 2019 – Oral presentation
• P.J.S. Rana, M. Fievez, T.M. Koh, M. Manceau, J.H. Lew, N.F. Jamaludin, B. Ghosh, A. Bruno, S. Cros, S. Berson, S.G. Mhaisalkar, W.L. Leong, “Scalable Slot-die Coating of FA1-xCsxPb(I1-yBry)3 Perovskite Solar Cells for High-Performance in Open Atmosphere”, ICMAT, Singapore, 2019 – Best poster award