Organosoluble starch derivative as quasi-solid electrolytes in DSSC: Unravelling the synergy between electrolyte rheology and photovoltaic properties

A novel blend of organosoluble phthaloyl starch (PhSt) and hydroxyethyl cellulose (HEC) was used as the polymer host to fabricate polymer gel electrolytes. Rheological analyses, such as amplitude sweep studies and tack tests, indicate that gels with good rigidity, strength and adhesiveness were attained upon inclusion of 20 wt % of HEC onwards. However, beyond 60 wt% of HEC, the mechanical properties and ionic conductivity of the gels were considerably compromised. Gels comprising 20-60 wt% of HEC were then fabricated into quasi-solid dye-sensitised solar cells (QSDSSC) with the addition of tetrapropylammonium iodide/iodine. The highest efficiency of 3.02% was recorded with gels comprising 70 wt% of PhSt and 30 wt% of HEC, which to the best of our knowledge is the highest ever efficiency in literature for starch-based electrolytes. Electrochemical impedance spectroscopy (EIS) of the QSDSSC revealed that the adhesive property of the gels plays a crucial role in charge transfer processes at the electrode/electrolyte interfaces.