Highly improved photocurrent and stability of dye-sensitized solar cell through quasi-solid-state electrolyte formed by two low molecular mass organogelators

A well-organized quasi-solid-state electrolyte is formed by binary mixtures of bisamide and valine as co-gelator via intermolecular hydrogen bonds. It is interesting that the ratio of the two components of quasi-solid-state electrolyte can be tuned to shift the position of TiO₂ conduction band edge, which can obviously enhance the driving force of electron injection process. Consequently, compared with the liquid electrolyte based dye-sensitized solar cell DSSC, the short-circuit current density (J_sc) of solar cellassembled by this quasi-solid-state electrolyte is increased about 12%. Moreover, the intensity-modulated photocurrent spectroscopy/intensity-modulated photovoltage spectroscopy (IMPS/IMVS) and electrochemical impedance spectroscopy (EIS) are carried out to investigate the influences of gelation on the kinetic processes of electron transport and recombination in DSSC. It is found that with the increasing of valine, the 3D network of quasi-solid-state electrolyte becomes looser and the electron transportation process is accelerated, meanwhile, the electron recombination lifetime is prolonged. As result, the quasi-solid-state solar cells (QS-DSSCs) employed with the bi-component quasi-solid-state electrolytes obtained a higher efficiency of 6.1% at AM 1.5 (100 mW cm²), but the efficiency of QS-DSSC based on the unitary component quasi-solid-state electrolyte formed by bisamide is only 5.3%. More importantly, these QS-DSSCs exhibit more excellent photo-thermal stability than the liquid electrolyte based DSSC.