Microstructural and chemical variation of TiO2 electrodes in DSSCs after ethanol vapour treatment

TiO2 based dye-sensitized solar cells (DSSCs) have great potential to solve many energy challenges, however, their low energy conversion rate is still a barrier for further applications. Ethanol vapour post-treatment can improve the DSSC's conversion efficiency without changing its architecture, and a stable 2–3% improvement was found in our experiments. Microstructural and chemical factors were investigated using scanning electron microscopy and analytical electron microscopy on treated and untreated electrodes. The vapour treatment improved the porosity and surface-to-volume ratio of the TiO2 particles, decreased electron transport loss between TiO2 and fluorine doped tin oxide, and increased hydroxyl sites on the TiO2 particle's surface. The modification therefore enhanced the dye uptake and dye–TiO2 coupling, and it reduced the energy loss during the carrier transfer.

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► A simple ethanol vapour post-treatment was applied to the TiO2 electrode in a DSSC.
► A stable efficiency improvement was evident after this post-treatment.
► Structural and chemical modifications of the treatment were systematically investigated using advanced electron microscopy.
► Morphology changes in favour of the efficiency improvement were identified (increased porosity and reduced TiO2 particle size).
► EELS study confirmed that stronger coupling formed between the dye and the treated TiO2.