Benzonitrile based electrolytes for best operation of dye sensitized solar cells Alessandro Latini * , Fadi Kamal Aldibaja, Carmen Cavallo, Daniele Gozzi Dipartimento di Chimica, Universit a di Roma La Sapienza, Piazzale Aldo Moro 5, 00185 Roma, Italy highlights  We developed new high performance electrolytes for dye sensitized solar cells.  These compositions are based on benzonitrile and non volatile.  These electrolytes show high stability over time under natural sunlight.  Efficiencies >8% can be achieved with common N719 dye and without coadsorbents. article info Article history: Received 2 April 2014 Received in revised form 4 June 2014 Accepted 27 June 2014 Available online 7 July 2014 Keywords: Dye-sensitized solar cells Non-volatile electrolyte Benzonitrile 3-Methoxypropionitrile abstract The beneficial effect of benzonitrile as electrolyte solvent in Dye Sensitized Solar Cells (DSSCs) is demonstrated. The very low vapour pressure of benzonitrile (133 Pa @ 25  C) ensures long-term stability to the cells and efficiency values were found around 8% for more than 1300 hours. These results were obtained by using commercial P90 titania photoanodes sensitized by N719 dye, i.e., by making use of common and low priced materials. In this way, neither complex dyes nor passivating agents are required to maintain satisfactory efficiencies in a non-volatile electrolyte solvent as 3-methoxypropionitrile, as reported in literature. The results of this work have to be considered an important step towards an easy and economic fabrication of devices with stable performances for commercially convenient periods. Twelve electrolytes were examined: 9 of them had benzonitrile as solvent, different ratios I - /I 2 and different ionic liquid iodide salts whereas, for comparison, one electrolyte in acetonitrile and another in 3-methoxypropionitrile were studied. As reference, the redox couple I  3 =I  in benzonitrile without ad- ditives was also examined. The electrolytes were characterized by specific conductivity vs. temperature, diffusion coefficient of I 3  and redox potential of the I  3 =I  couple measurements. Efficiency, dark current and IPCE of DSSCs were determined for each electrolyte. © 2014 Elsevier B.V. All rights reserved. 1. Introduction In a recent paper [1] we obtained a reproducible behaviour and a significant improvement of the efficiency of dye sensitized solar cells by the substitution of pure anatase semiconductor in the photoanode with solid solutions of scandium in anatase. Changing the photoanode semiconductor only and making a great effort to maintain everything else in the cell unchanged, these results were obtained. It is well known that several factors influence the DSSC performances, very often in an unpredictable way, so it is always good practice to try to maintain as invariant as possible all the components of the cells except that one we are interested to study. This appears to be a trivial issue but if a strict and controlled pro- tocol is not enforced the final result can be unreliable. With this basic rule, the present and past works [1,2] were carefully performed. It is frequently reported in literature [3,4] that the environment in which the redox couple I  3 =I  is contained plays an important role in the optimum operation of the cell. The environment and the redox couple are as whole the electrolyte in which the mobility of I  3 species should be as high as possible in order to be reduced at counter electrode and a fast regeneration of the dye, D, through the 3I  þ 2D þ ¼ 2D þ I  3 reaction at photoanode. Some key parameters can affect significantly the I  3 mobility: i. solvent properties (vis- cosity, dielectric constant, dipole moment, donor number, good * Corresponding author. Tel./fax: þ39 0649913161. E-mail address: alessandro.latini@uniroma1.it (A. Latini). Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour http://dx.doi.org/10.1016/j.jpowsour.2014.06.154 0378-7753/© 2014 Elsevier B.V. All rights reserved. Journal of Power Sources 269 (2014) 308e316