sol–gel approach for the growth of vertically aligned 3d-tio2 nanorod arrays as an efficient photoanode for high-performance dye-sensitized solar cells

In this study, a facile, low cost, and scalable sol–gel method has been proposed for the coating of ultra-thin layer of tio2 on fto substrate as a seed layer for the growth of 3d-tio2 nanorod (3d-tio2-nr) arrays on fto. then, the two-step hydrothermal process including nanorod growth and the chemical etching treatment was proceeded for the fabrication of fto/3d-tio2-nr photoanodes. the thickness of the deposited tio2 in fto/tio2-sg samples was measured with small-angle x-ray scattering technique, and it was obtained to be 21.3 nm. fe-sem and tem techniques were used for the morphological characterization of 3d-tio2-nr, and it was obtained that the tightly adhered film of vertically aligned 3d-tio2-nr with two-layer nanostructuring is formed with a cubic base and a nanorods head. finally, dsscs with iodine-based and cobalt(ii/iii) tris(2,2′-bipyridine) complex-based electrolytes with two different photoanodes including 3d-tio2-nr and tio2-np were assembled and their photovoltaic characteristics were investigated. for [co(bpy)3]2+/3+ shuttle-based dssc, the obtained power conversion efficiency (η) was about 3.5% with jsc of 9.36 ma cm−2 in 3d-tio2-nr-based dssc, while η of tio2-np-based dssc was about 1.4%. the results showed that employing 3d-tio2-nr-based photoanode in dsscs with bulky electron shuttles remarkably improves the photovoltaic characteristics of dsscs. electrochemical impedance spectroscopic studies also showed the lower charge transfer resistances for dsscs with nanorod-based photoanode building blocks.