A new approach to understanding the deficiency of backside illuminated dye-sensitized solar cells’ fill factor as a result of cracking of the TNAs

Abstract

Abstract In this work, a new approach was taken to gain an insight into the deficiency of backside illuminated dye-sensitized solar cells’ fill factor as a result of cracking of the TNAs. In order to obtain cracked and non-cracked TNAs and compare their properties and performance in backside illuminated DSSCs, anodization was carried out respectively using pretreated Ti substrates covered with TiO2 nanoparticles and bare Ti substrates. To cover the Ti substrates with 20-30 nanometer-sized TiO2 nanoparticles, they were conventionally TiCl4 treated. The SEM images of the anodized TNAs approved the sever and wide cracking of the TNAs grown on TiCl4 treated Ti substrates compared to those of grown on bare Ti substrates. The reason for this phenomenon could be the accumulation and stacking of the nanoparticles among the bundles of the TNAs. It is approved by narrower peaks of the XRD patterns for TiCl4 treated TNAs and the observed stacks of nanoparticles in the intersectional SEM images. The anodized TNAs grown both on TiCl4 treated and bare Ti substrates were applied as photoanodes in backside illuminated DSSCs. All the photovoltaic parameters other than fill factor and the consequent efficiency obtained from both the grown TNAs on TiCl4 treated and bare Ti substrates were equal. Whereas, the fill factor and efficiency of the DSSCs using cracked TNAs (grown on TiCl4 treated Ti substrates) were approximately 9% lower. This deficiency of the DSSCs is attributed to the presence of the nanoparticles and cracking of the TNAs which result in an increase of series resistance in the cell.