Composite electrolytes of polyethylene glycol methyl ether and TiO2 for dye-sensitized solar cells—Effect of heat treatment

For solid-state dye-sensitized solar cells (DSSCs), a composite electrolyte of polyethylene glycol methyl ether (PEGME) and titania (TiO2) nanoparticles was prepared and characterized by Fourier transform-infra red (FT-IR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Raman spectroscopy. The heat treatment on PEGME and TiO2 composite was found to be an essential step to improve morphology, amorphicity and ionic conductivity of PEGME–TiO2 composite electrolytes. It was attributed to the increased bond strength of OC–O–Ti between PEGME and TiO2 and increased surface roughness of composite materials, which may help to absorb a large amount of iodide couple and effective generation of I3− ions. A DSSC fabricated with heat treated PEGME–TiO2 composite electrolyte showed significantly enhanced overall conversion efficiency of 3.1%, which was 20% higher than that of the DSSC fabricated with bare PEGME–TiO2 composite electrolyte.