P-type Oxide senSITIzation For tandem dye-sensitized solar cells – POSITIF

To lift up the above challenge, the preparation of nanoparticles of new p-SCs and the comprehensive understanding of their electronic properties are under way. One main objective is to replace the most commonly used p-SC which is NiO by new materials exhibiting better suited characteristics. Several preparation methods of the oxides nanoparticles are employed such as wet chemistry, electrosynthesis and pulse layer deposition (PLD). This program will explore the development of new methods of p-SCs preparation and new materials specially designed for p-DSSC (SC-p, dyes and redox mediators). Another aspect of the program is the synthesis of new sensitizers especially designed for p-DSSCs. Ultimately, the new materials will be used to prepare tandem DSSCs. This project gathers several teams including an industrial partner with 5 major skills: solid-state chemistry, organic synthesis, photophysics, electrochemistry and quantum chemistry calculations. This multidisciplinary project represents an important scientific challenge and could lead to the rational development of new photovoltaic cells and more importantly, new tandem DSSCs whose efficiency could be higher than that of conventional Gratzel cells.

As far as the dyes are concerned, we have developed with success the synthesis of many new sensitizers and most importantly discovered new families with high photovoltaic performances, which are above than that of the reference and highly performing P1 dye.
We have experimentally demonstrated that simple dyes (without secondary electron acceptor) can lead to long lived charge separated state on NiO situated in the range of few microseconds.
As far as the semiconductors are concerned, we have developed a new deposition technique of NiOx layer by electrochemical method. We have achieved the reproducible synthesis of nanoparticles of CuGaO2 doped with Mg with a good control of the surface area. The increased conductivity of CuGaO2 doped with Mg has been realized with success. The origin of the dark black color of NiO films has been elucidated for the first time.
An easy deposition technique of the co-adsorbate CDCA on NiO has enabled to importantly limit the dark current and to access to high Voc (above 500 mV) with classical materials (NiO, cobalt electrolyte and dyes).
The photophysical measurements by transient absorption spectroscopy and the numerous quantum chemical calculations have enabled to draw a better understanding of the photovoltaic performances of the dyes and particularly of the porphyrin sensitizers, which are dominated by unusually ultra-fast geminate charge recombination.

The first tandem DSSCs were build delivering a Voc over 1 V

The perspectives focus on the preparation of new semiconductors for which the photocurrent density will be higher, because this is currently the main limitation that we are facing.

(1) Favereau, L.; Warnan, J.; Pellegrin, Y.; Blart, E.; Boujtita, M.; Jacquemin, D.; Odobel, F Chem. Commun. 2013, 49, 8018-8020.

(2) Herraiz-Cardona, I.; Fabregat-Santiago, F.; Renaud, A.; Julián-López, B.; Odobel, F.; Cario, L.; Jobic, S.; Giménez, S Electrochim. Acta 2013, 113, 570-574
(3) Renaud, A.; Chavillon, B.; Cario, L.; Le Pleux, L.; Szuwarski, N.; Pellegrin, Y.; Blart, E.; Gautron, E.; Odobel, F.; Jobic, S., J. Phys. Chem. C 2013, 117, 22478-22483.
(4) Odobel, F.; Pellegrin, Y.: J. Phys. Chem. Lett. 2013, 4, 2551-2564.

(5) Renaud, A.; Cario, L.; Deniard, P.; Gautron, E.; Rocquefelte, X.; Pellegrin, Y.; Blart, E.; Odobel, F.; Jobic, S.: J. Phys. Chem. C 2014, 118, 54-59.
(6) Gennari, M.; Légalité, F.; Zhang, L.; Pellegrin, Y.; Blart, E.; Fortage, J.; Brown, A. M.; Deronzier, A.; Collomb, M.-N.; Boujtita, M.; Jacquemin, D.; Hammarström, L.; Odobel, F J. Phys. Chem. Lett. 2014, 5, 2254-2258.
(7) Warnan, J.; Pellegrin, Y.; Blart, E.; Zhang, L.; Brown, A.; Hammarström, L.; Jacquemin, D.; Odobel, F.: Dyes & Pigments 2014, 105, 174-179.

(8) Gennari, M.; Légalité, F.; Zhang, L.; Pellegrin, Y.; Blart, E.; Fortage, J.; Brown, A. M.; Deronzier, A.; Collomb, M.-N.; Boujtita, M.; Jacquemin, D.; Hammarström, L.; Odobel, FJ. Phys. Chem. Lett. 2014, 5, 2254-2258.
(9) A. Renaud, L. Cario, Y. Pellegrin, E. Blart, M. Boujtita, F. Odobel, S. Jobic, RSC Adv., 2015, 5, 60148-60151

(10) Maufroy, A.; Favereau, L.; Anne, F. B.; Pellegrin, Y.; Blart, E.; Hissler, M.; Jacquemin, D.; Odobel, F.: J. Mater. Chem. A 2015, 3, 3908-3917.
(11) Ameline, D.; Diring, S.; Farre, Y.; Pellegrin, Y.; Naponiello, G.; Blart, E.; Charrier, B.; Dini, D.; Jacquemin, D.; Odobel, F RSC Adv. 2015, 5, 85530-85539.

There are currently many studies on the photosensitization of “n-type” semiconductors with view to developing photovoltaic devices (usually known as Grätzel cells or dye-sensitized solar cells). The common feature of these photo-electrochemical devices lies in the fact that the photoexcited state works as an electron donor into the conduction band of an “n-type” semiconductor. The proposed project concerns a new technology, namely the photosensitization of “p-type” semiconductors (p-SCs) by photoinjection of holes into their valence band (VB).
In this program, we propose to make a major breakthrough in this area by replacing nickel oxide (almost the sole p-SC used for this technology) with alternative metal oxides (doped zinc oxide, delafossites, oxychalcogenides with rare earth elements and copper) and preparing optimized sensitizers, which would offer a higher photoconversion efficiency. To lift up this challenge, the preparation of nanoparticles of new p-SCs and the comprehensive understanding of their electronic properties are crucial. We initiated this program in 2004, and our first studies led us to successfully prepare nanostructured CuGaO2 and LaOCuS which are among the most conductive p-SCs known so far. This initial study provides a first proof of concept of the operational p-DSSC with oxide other than NiO and of the feasibility and potentiality of tandem cells. This program will explore the development of new methods of p-SC preparations and the suitability of new materials specially designed for p-DSSC (SC-p, dyes and redox mediators). This project gathers several teams, including an industrial partner, with 5 major skills: solid-state chemistry, organic synthesis, photophysics, electrochemistry and quantum chemistry calculations. This multidisciplinary project represents an important scientific challenge and could lead to the rational development of new photovoltaic cells and more importantly, new tandem DSSCs with cost/efficiency ratio which could compete with existing technologies.