Substrate Diameter-Dependent Photovoltaic Performance of Flexible Fiber-Type Dye-Sensitized Solar Cells with TiO2 Nanoparticle/TiO2 Nanotube Array Photoanodes

Fiber-type dye-sensitized solar cells (FDSSCs) are attractive as an energy source of soft electronics due to low-costs, non-toxicity and especially, their indoor-weak-light workable features. The TiO2 nanotube array (TNA) can grow on flexible Ti wires directly using anodization technique, which is convenient and can provide better contact between substrate/TiO2. However, a systematic study of assembling efficient TNA on photoanode of FDSSC is limited. This study investigated the anodization voltage and time effects of growing TNA on Ti wires. TiO2 nanoparticles (TNP) are fabricated on TNA using dip-coating technique to compensate for low dye adsorption of TNA. Dip-coating rate is varied to optimize TNP thicknesses to provide effective dye adsorption and charge-transfer routes. The highest photon-to-electricity conversion efficiency (eta) of 3.31% was obtained for FDSSCs with TNA/TNP photoanode prepared using 60 V as the anodization voltage and 40 cm/min as the dip-coating rate. The influence of titanium wire diameter on eta of FDSSCs was studied. The bending test was carried out on flexible FDSSC assembled using plastic tube. The photocurrent retention of 84% is achieved for flexible FDSSC bended for 10 times. This work firstly provides facile ways to assemble efficient photoanode with composite TiO2 structures for FDSSC and opens new insights on studying titanium wire natures on FDSSC performance.