Wednesday, 3 October 2018
Universal Ballroom (Expo Center)
Dye-sensitized solar cells (DSCs) combines benefits of low-cost, simple fabrication and competitive solar energy conversion efficiency. Recent success in the replacement of traditional iodide/tri-iodide redox mediators by noncorrosive, less light absorption cobalt (II/III) polypyridyl complexes has led to encouraging solar energy conversion efficiencies in excess of 13%, well beyond that of iodide/tri-iodide based electrolytes (ca.11%). Solvent evaporation in traditional liquid electrolyte challenges durable encapsulation of DSCs. This has driven increasing focus on alternative semi-solid-state electrolytes for practical DSC applications. Gel electrolytes have exhibited an impressive long-term stability, especially for outdoor applications where temperature of the DSC system can reach 80-85 oC under sunlight. In a solid-state gel electrolyte, the mass transport of cobalt (II/III) complexes is greatly retarded by the highly viscous gelatinous environment, which limits the dye regeneration and thus the overall efficiency of the SS-DSCs. To date, there are still very limited reports of this new type of SS-DSCs, leaving great scope for further development. Sophisticated architectural designs that leverage macro-porosity to promote ionic diffusion and meso-porosity to increase specific surface area for dye loading may also provide a viable solution to tackle the current limit in cobalt gel electrolyte based SS-DSCs, leading to a higher efficiency [1]. In this work, we establish that a simple replacement of photoanode building-blocks from standard commercial TiO2 nanoparticles (CCIC and P25) to titania nanorod aggregates (TNA) enabled remarkable improvement on ionic diffusion of cobalt (II/III) tris(2′2-bipyridine) complexes in a gel electrolyte. An overall solar energy conversion efficiency of over 7.1% and 8.0% was reached by freshly constructed and stabilized SS-DSCs using the TNA, respectively. Those correspond to efficiency enhancements up to 35% and 100% against that of the standard TiO2 nanoparticles – P25 (4.0%) and CCIC (5.9%), respectively.