Fabrication of High Efficiency Dye-Sensitised Solar Cell with Zirconia-Doped TiO2 Nanoparticle and Nanowire Composite Photoanode Film

Abstract

Dye-sensitised solar cells (DSSCs) were fabricated based on coumarin NKX-2700 dye-sensitised zirconia-doped TiO2 nanoparticle and nanowire composite photoanode film and quasi-solid-state electrolyte, sandwiched together with cobalt sulfide-coated counter electrode. Novel photoanodes were prepared using composite mixtures of 90 wt-% TiO2 nanoparticles + 10 wt-% TiO2 nanowires (TNPWs) as base material and zirconia as doping metal. Hafnium oxide (HfO2) was applied on the zirconia-doped TNPWs (zirconia/TNPWs) film structure as a blocking layer. TiO2 nanoparticles, TiO2 nanowires, and zirconia/TNPWs were characterised by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The sensitising organic dye coumarin, NKX-2700, displayed maximum absorption wavelength (λmax) at 525 nm, which could be observed from the UV-visible spectrum. DSSC-1 built with zirconia/TNPWs-doped photoanode with blocking layer revealed enhanced photo-current efficiency (PCE) as compared with other DSSCs and illustrated photovoltaic parameters: short circuit current JSC = 20 mA m–2, open circuit voltage (VOC = 730 mV, fill factor (FF) = 68 %, and PCE (η) = 9.93 %. The electron transport and charge recombination behaviours of DSSCs were investigated by electrochemical impedance spectroscopy and the results exhibited that DSSC-1 possessed the lowest charge transfer resistance (Rrec) and longest electron lifetime (τrec) compared with other DSSCs. Therefore, from the present investigation, it could be concluded that the improved performance of DSSC-1 is ascribed to the zirconia/TNPWs-doped photoanode with the blocking layer increasing the short circuit current, electron transport, and suppressing the recombination of charge carriers at the photoanode/dye/electrolyte interface.