Vein graphite-based counter electrodes for dye-sensitized solar cells

[Display omitted] •Purified Sri Lankan vein graphite has been used as counter electrode material in dye-sensitized solar cells (DSCs).•We devised a novel technology for graphite enrichment in which the ball-milled Sri Lankan graphite (BMG) was floated in water.•Ball-milled floated graphite (BMFG) was separated and both BMG and BMFG were extensively characterized for the first time.•It has been found that the floating technology has increased the defect sites that act as catalytic sites for I3− reduction.•It has been found that BMFG is a better counter electrode material than BMG for applications in DSCs. This paper describes the use of ball-milled vein graphite and ball-milled floated graphite counter electrode (CE) materials in dye-sensitized solar cells. The vein graphite used was ball milled, sieved and fraction of particle sizes in the 45–63μm was used (BMG). Another fraction in the same size range was floated in water to get ball-milled floated graphite (BMFG). Both samples were extensively characterized by electrochemical techniques, Raman spectroscopy and by Total Carbon Analysis. The performance of dye-sensitized solar cells (DSCs) prepared using these CEs were optimized for their adhesion, sintering temperature and thickness. Best performances were obtained for the DSC with CE prepared using graphite:morphol mass ratio of 5:3, sintering temperature of 350°C and the thickness of 250μm. Most of the impurities in ball-milled graphite can be removed by the floating technique and the DSC fabricated with ball-milled floated graphite based CE gives 24% better performance than that constructed using just ball-milled graphite based CE. The best conversion efficiency observed is 6.47%. Though this is less than that obtained using Pt CE, it is still very useful in practical applications as per cost considerations.