Modification of nanocrystalline porous films by poly(ethyleneglycol) for quasi-solid dye-sensitized solar cells

A convenient way is experimented to reduce the amount of dye in quasi-solid DSSCs but raise open-circuit photovoltage and photocurrent density. AFM stereoscopic morphology and calculated roughness of root mean square indicates looser porous configuration is formed in the modified TiO2 film which is beneficial for the penetration of quasi-solid electrolyte. Decreased content of sensitized dye is confirmed by UV-vis absorption spectra. Electrochemical impedance spectroscopy is employed to characterize the transport and recombination of electrons and also to assess the penetration of quasi-solid electrolyte in the porous matrix of DSSCs. Analysis of charge-transfer resistance and dc resistance of impedance of diffusion of tri-iodide reveals enhanced mobility of tri-iodide in DSSCs. Photovoltaic parameters of quasi-solid DSSCs show an increased open-circuit photovoltage due to the enlarged photoelectrode film porosity and the shift of redox level. Better penetration of quasi-solid electrolyte has a predominant advantage over the negative effect caused by lose of photocurrent, to some extent, as a result of decreased adsorbed dye. The best result of this beneficial outcome occurs when the PEG loading is 20%, giving an overall cell efficiency of 5.1%. (C) 2011 Elsevier B.V. All rights reserved.