Enhanced performance of bi-layer Nb2O5 coated TiO2 nanoparticles/nanowires composite photoanode in dye-sensitized solar cells

•DSSCs were fabricated using TiO2 nanoparticle and nanowire composites (TNPWs) with Nb2O5/HfO2 nanoparticles as bilayer/blocking layer.•Coumarin NKX-2700 is used as sensitizer with quasi solid state electrolyte.•Efficiency has enhanced 36%.

Dye sensitized solar cells (DSSCs) were fabricated based on coumarin NKX-2700 dye sensitized bi-layer photoanode and quasi-solid state electrolyte sandwiched together with cobalt sulfide coated counter electrode. A novel bi-layer photoanode has been prepared using composite mixtures of 90 wt.% TiO2 nanoparticles + 10 wt.% TiO2 nanowires (TNPWs) as active layer and Nb2O5 is coated on the active layer, which acts as scattering layer. Hafnium oxide (HfO2) was applied over the TNPWs/Nb2O5 photoanode film, as a blocking layer. TiO2 nanoparticles (TNPs), TiO2 nanowires (TNWs) and TNPWs/Nb2O5 were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The sensitizing organic dye coumarin NKX-2700 displayed maximum absorption wavelength (λmax) at 525 nm, which could be observed from the UV–vis spectrum. DSSC-1 fabricated with composite bi-layer photoanode revealed enhanced photo-current efficiency (PCE) as compared to other DSSCs and illustrated photovoltaic parameters; short-circuit current JSC = 18 mA/cm2, open circuit voltage (VOC) = 700 mV, fill factor (FF) = 64% and PCE (η) = 8.06%. The electron transport and charge recombination behaviors of DSSCs were investigated by electrochemical impedance spectra (EIS) and the results illustrated that the DSSC-1 showed the lowest charge transport resistance (Rtr) and the longest electron lifetime (τeff). Therefore, in the present investigation, it could be concluded that the novel bi-layer photoanode with blocking layer increased the short circuit current, electron transport and suppressed the recombination of charge carriers at the photoanode/dye/electrolyte interface in DSSC-1.

Graphical abstractNovel high efficiency dye sensitized solar cell has been fabricated with photoanode of TiO2 nanoparticles and TiO2 nanowires with Nb2O5/HfO2 nanoparticles as bilayer/blocking layer.Figure optionsDownload full-size imageDownload high-quality image (116 K)Download as PowerPoint slide