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Ultrafast photoinduced processes of organic dyes in IL/molecular solvent mixtures designed for dye solar cells – UPPiL

Ultrafast photoinduced processes of organic dyes in IL/molecular solvent mixtures designed for dye sensitized solar cells

A minor change of solvent in the electrolyte of a dye-sensitized solar cell (DSSC) can dramatically influence its conversion efficiency and stability. Unfortunately, no explanation has yet been given for this crucial phenomenon. The UPPiL project exists to compensate for this lack of data. Understanding the effects of solvents on both photosensitizers and cells in operation is the reason to be of UPPiL.

unlock the power conversion efficiency of DSSCs by understanding the effects of solvents on the efficiency and stability of these devices.

By understanding the fundamental processes related to the solvents effects on the efficiency and stability of solar cells, UPPiL aims to provide the necessary knowledge to develop powerful dye-sensitized solar cells accessible to all. The aim is to study the photosensitizer / electrolyte interaction which controls the conversion efficiency and the stability of DSSCs. The originality of UPPiL is to study this fundamental interaction by combining time-resolved spectroscopy techniques (from microsecond to femtoseconde) with theoretical calculations / molecular dynamics simulations as well as with photovoltaic measurements, all on operating solar cells.

The approach consists in a double study: study the fundamental photophysical processes that govern three classes of photosensitizers by time-resolved spectroscopy techniques and by molecular dynamics. This part is built of two parts: a study of solvation dynamics in ionic liquid / molecular solvent mixtures and a study of the photodynamics of dyes. The second approach, more applicative, consists in combining time-resolved spectroscopy measurements with photovoltaic measurements in solar cells with different operating modes. This dual approach makes it possible to produce scientific results in three areas: spectroscopy, theoretical calculations and photovoltaic.

Regarding the solvation dynamics in ionic liquid / molecular solvent mixtures (WP1): we were able to isolate the different components of ionic liquid / molecular solvent mixtures that influence solvation responses for the different part of the solvation response. We now have, thanks to the combination of time-resolved manipulations and molecular dynamics, a clear image of the solvation processes in these mixtures which will be able to shed light on the photoelectric phenomena that can take place in particular in solar cells but also in supercapacitors or batteries.
Considering the photodynamics of photosensitizers in solution (WP2), we are in the process of characterizing several emissive species for the chosen photosensitizers. These results could influence the adsorption efficiency of the dyes on the TiO2 electrode. These emissive species are being identified right now in my team. Theoretical calculations are also performed to identify these species.
Results on measurements in solar cells (WP3) are in progress with the LRCS. They will make it possible to better define the relationship between photochemical signal originating from fundamental processes within the cell and transient electrical signal produced by this same cell with different operating modes.

The results in fundamental photochemistry being mainly launched and a routine having been acquired for the WP1 and WP2.
We are therefore focusing our efforts on WP3, the most ambitious and promising work package, but also the most demanding in terms of time and work, since it consists of these combined measurements in photovoltaics and time-resolved spectroscopy. It requires both LASIRE and LRCS resources.

3 publications submitted on WP1 with one implying all the members of the porject,.and one chapter of a book sent also. There are also 2 more publications in preparation. :
1. A new key feature about the mechanism of the solvation dynamics in BmimBF4/PC mixtures: a cooperative study employing time-resolved ?uorescence and molecular dynamics
Yevheniia Smortsova, François-Alexandre Miannay,*, Thomas Gustavsson, Frédéric Sauvage, Francesca Ingrosso, Oleg Kalugin, Abdenacer Idrissi*, soumis à JMolLiq ;
2. Effect of Acetonitrile Solution on Structure, Conformational Dynamics and Electronic Spectra of D205 Indoline Dye Anchored to Small TiO2-Anatase Nanoparticle, Miannay, Idrissi, soumis à Journal of molecular simulation ;
3. Descriptors of the charge transfer of Coumarin in C4mimBF4/acetonitrile mixture : A quantum calculation analysis, Mohammed Arab Ait Tayeb, Noureddine Tchouar, François Alexandre Miannay and Abdenacer Idrissi, soumis à JMolLiq

1 chapter: Local structure in a mixture of ionic liquid with molecular solvent : vibration spectroscopy, NMR and Molecumar dynamics simulation, Idrissi, Miannay, envoyé à elsevier Science book.

Among all the renewable energy sources, solar energy is the most powerful source far ahead wind or geothermal energies. The possibility of an efficient and low-cost direct conversion of the sunlight energy into electricity is a clear scientific and technological stakes. Dye-sensitized solar cell (DSSC) is a type of thin film solar cell. It provides a technically and economically viable concept. The state-of-the-art DSSCs' low efficiency and instability are the shortcomings of these promising devices. The foundation of UPPiL emerged from an important observation: changing the solvent of electrolytes may reduce drastically the power efficiency and affect the stability of DSSCs. Which dye/solvent interaction dominates these profound effects? What are the molecular rearrangements in the solvents of electrolytes influencing the stability and the efficiency? To answer this problematic, UPPiL aims at studying the effect of solvents of electrolytes (solvation dynamics) on the efficiency and on the long-term stability of DSSCs. UPPiL proposes to use a new class of tuneable media/solvents for electrolytes combined with three state-of-the-art sensitizers in DSSCs. UPPiL will take 2 steps (i) the study of the molecular rearrangements of solvent around the sensitizer after the photoexcitation and (ii) the simultaneous monitoring of time-resolved spectroscopic and electrical characteristics of DSSCs. UPPiL works at two interfaces: the interface of experimental with theoretical for the solvent’s characteristics investigations and the interface of ultrafast photophysical processes of the sensitizers (electron injection, regeneration) with transient electrical signals of DSSCs. UPPiL will benefit from the high degree of competence of LASIR in ultrafast time-resolved spectroscopy and will call upon the high expertise of LRCS in the realm of DSSCs conception and characterization. Indeed, LASIR is one of the largest time-resolved spectroscopy platforms in Europe (Raman, infrared, UV-Vis, fluorescence) and LRCS is a photovoltaic unit, recognized at the European level. Starting from our previous observations and generating new types of results, UPPiL will pave the way to new sensitizers and new optimized solvents development allowing the conception of high efficiency and long-term stability DSSCs.

Project coordination

François-Alexandre MIANNAY (Laboratoire de Spectrochimie Infrarouge et Raman)

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

LASIR Laboratoire de Spectrochimie Infrarouge et Raman

Help of the ANR 178,848 euros
Beginning and duration of the scientific project: September 2019 - 36 Months

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