Imbibition of polypyrrole into three-dimensional poly(hydroxyethyl methacrylate/glycerol) gel electrolyte for robust quasi-solid-state dye-sensitized solar cells

Hydrophobic poly(hydroxyethyl methacrylate/glycerol) [poly(HEMA/GR)] gel with a three-dimensional (3D) framework was successfully fabricated and employed to integrate with polypyrrole (PPy). The resultant PPy imbibed poly(HEMA/GR) gel electrolyte exhibited interconnective porous structure for holding I-/I-3(-), giving a similar conduction mechanism and ionic conductivity to that of a liquid system but a much enhanced retention of I-/I-3(-) redox couple. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction technique, Tafel-polarization measurements as well as electrochemical impedance spectroscopy were employed to evaluate the morphology, molecular structure, crystallinity, and the electrochemical behaviors. The results showed that the combination of PPy with poly(HEMA/GR) caused a lower charge-transfer resistance and higher electrocatalytic activity for the I-/I-3(-) redox reaction in the gel electrolyte. The resultant quasi-solid-state dye-sensitized solar cells based on PPy imbibed poly(HEMA/GR) gel electrolyte gave an overall light-to-electric conversion efficiency of 6.63%.