Hierarchical micro/nano-structured titanium nitride spheres as a high-performance counter electrode for a dye-sensitized solar cell

Hierarchical micro/nano-structured TiN spheres (micro/nano-TiNs) counter electrodes are fabricated by coating hierarchical micro/nano-TiO2 paste onto Ti foil followed by a nitridation reaction. Compared with particulate TiN and TiN flat electrodes, the as-prepared hierarchical micro/nano-TiNs electrode based dye-sensitized solar cells (DSCs) delivers significantly improved photovoltaic performances due to the presence of the hierarchical structure. In particular, V-OC is enhanced by about 60 mV, which may be predominantly attributed to the gaining of favourable interfacial active sites and the traces of N-doped carbon residues. After an initial optimization of the particle sizes of the hierarchical micro/nano-TiNs, the reflectance effect of large submicroscale particles is attempted to improve the I-SC. The highest overall conversion efficiency yields 7.83%, which is 30% higher than that of Pt/FTO (6.04%).