Electrophoretic deposition of graphene-TiO₂2 hierarchical spheres onto Ti thread for flexible fiber-shaped dye-sensitized solar cells

Highlights: • Graphene-TiO₂ composite is deposited onto Ti thread by electrophoretic deposition. • They are used as photoanodes of fiber-shaped dye-sensitized solar cells. • Our work may establish an industrial procedure to produce fiber-shaped solar cells. A multiple electrophoretic deposition (EPD) technique is developed to deposit complicated hierarchical TiO₂ spheres and graphene-TiO₂ spheres composite onto flexible Ti thread as working electrode of fiber-shaped dye-sensitized solar cells (F-DSSCs). Experimental results show that this multiple EPD technique cannot only fill up the cracks coming from drying the previous single EPD film but also adjust the thickness of films. More importantly, this approach is adaptable to build both single material and more complicated composite on the fiber-shaped substrates. With this technique, high quality graphene-TiO₂ film is acquired on flexible Ti thread and F-DSSCs based on 0.3 wt.% graphene-TiO₂ hierarchical spheres show a remarkable enhancement in conversion efficiency (2.68%) compared to that of bare TiO₂ hierarchical spheres (1.50%). Further TiCl₄ solution treatment of 0.3 wt.% graphene-TiO₂ photoanode achieves device efficiency of 3.26% resulting from the improved connectivity between the particles in the film. Our work may establish an industrial procedure to produce complex hierarchical architecture on the high curvature surface of the flexible substrates with broader range of practical application.