Impact of isoelectric points of nanopowders in electrolytes on electrochemical characteristics of dye sensitized solar cells

Nanoparticle loaded quasi solid electrolytes are important from the view point of developing electrolytes for dye sensitized solar cells (DSSCs) having long term stability. The present work shows the influence of isoelectric point of nanopowders in electrolyte on the photoelectrochemical characteristics of DSSCs. Electrolytes with nanopowders of silica, alumina and magnesia which have widely differing isoelectric points are used in the study. Adsorption of ions from the electrolyte on the nanopowder surface, characterized by zeta potential measurement, show that cations get adsorbed on silica, alumina surface while anions get adsorbed on magnesia surface. The electrochemical characteristics of nanoparticulate loaded electrolytes are examined through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). DSSCs fabricated using liquid, silica or alumina loaded electrolytes exhibit almost similar performance. But interestingly, the magnesia loaded electrolyte-based cell show lower short circuit current density (J(SC)) and much higher open circuit voltage (V-OC), which is attributed to adsorption of anions. Such anionic adsorption prevents the dark reaction in magnesia loaded electrolyte-based cell and thus, enhances the V-OC by almost 100 mV as compared to liquid electrolyte based cell. Also, higher electron life time at the titania/electrolyte interface is observed in magnesia loaded electrolyte-based cell as compared to others. (C) 2012 Elsevier B.V. All rights reserved.