A novel multilayered photoelectrode with nitrogen doped TiO2 for efficiency enhancement in dye sensitized solar cells

Nitrogen doped TiO2 powder samples were synthesized by a modified wet chemical method using aqueous ammonia and nitrogen gas purged on titanium tetra isopropoxide (TTIP). Photolectrodes with different combinations of layers of nitrogen ? doped TiO2, undoped TiO2 and Degussa P25 TiO2 powders were used in dye sensitized solar cells (DSSCs). The highest conversion efficiency of 8.00% was achieved by the cells fabricated with compact layer/P25/N-doped TiO2 multilayer photoelectrode. This is an impressive enhancement in efficiency close to 89% with respect to a similar multilayer electrode made with undoped TiO2 which showed a conversion efficiency of 4.22%. The enhancement in the efficiency appears to be due to the increased photocurrent density of the DSSCs resulting mainly from energy band gap narrowing due to N-doping with some contribution from increased dye uptake by the novel multilayer electrode. These results have been substantiated by the reduced charge transfer resistance obtained from Electrochemical Impedance Spectra and the enhanced IPCE spectra of the DSSCs with N-doped TiO2 based multilayer electrode

Solid-state solar cells co-sensitized with PbS/CdS quantum dots and N719 dye and based on solid polymer electrolyte with binary cations and nanofillers

Co-sensitized solar cells have gained more attention due to the ability of energy conversion process by absorbing photons from wide range of the solar spectrum including visible and near-infrared region. TiO2 electrodes were co-sensitized with PbS/CdS core-shell quantum dots and N719 dye. PbS/CdS/N719 dye-sensitized solar cells were fabricated with poly(ethylene oxide) based solid polymer electrolyte consisting iodide/triiodide redox couple. The iodide ion conductivity of the electrolyte was enhanced by incorporating a binary iodide salt mixture of different size cations, tetrapropylammonium iodide and potassium iodide. The performance of the solar cell was further enhanced by the incorporating TiO2 P90 nanofiller in the electrolyte. The best solid-state solar cell showed a significantly higher efficiency of 4.41 % with a short-circuit current density of 8.41 mA cm−2, open-circuit voltage of 748.3 mV and a high fill factor of 70.16 % under the simulated light of 100 mW cm−2 with AM 1.5 filter. This is the first report describing the efficiency enhancement in a solid-state dye sensitized solar cell based on a solid polymer electrolyte incorporating a binary cation iodide salt and TiO2 nanofiller and a photoanode co-sensitized with PbS/CdS quantum dots and N719 dye demonstrating the cumulative effect by the mixed cation effect and co-sensitization

Morphological and structural study on low cost SnO2 counter electrode and its applications in quantum dot sensitized solar cells with polysulfide electrolyte

Fabrication of efficient CdS quantum dot sensitized solar cell with a novel stable counter electrode based on a thin film of SnO2 is revealed. The film was characterized by using Scanning Electron Microscopy (SEM), High-Resolution Tunneling Microscopy, X-ray diffraction (XRD) and UV–Visible spectroscopic techniques. Photovoltaic performances and Electrochemical Impedance Spectroscopic techniques (EIS) were performed on FTO/TiO2/CdS/polysulfide/SnO2/FTO device under the light illumination of 100 mW cm−2 and comparison was done with the conventional Pt counter electrode. Impressive 43 % efficiency enhancement in these solar cells was achieved compared with the Pt based devices. Porous thick nanostructure of SnO2 with crystal defects such as oxygen vacancies and Sn vacancies arising from lattice structures as confirmed by SEM, Raman and, XRD spectroscopy could be some of the reasons for this enhancement. Excellent photo enhanced electrocatalytic activity against the polysulfide electrolyte is confirmed by EIS and Cyclic Voltammetry studies.</p

Efficiency enhancement in dye-sensitized solar cells with co-sensitized, triple layered photoanode by enhanced light scattering and spectral responses

Abstract: A method for impressive efficiency enhancement in TiO2-based nanoparticle (NP) dye-sensitized solar cells (DSSCs) is demonstrated by using a co-sensitized triple layered photoanode, comprising a nanofibre (NF) layer of TiO2 sandwiched between two TiO2 P25 NP layers. Rose Bengal (RB) and Eosin-Y (EY) dyes are used for the co-sensitization. DSSCs with conventional TiO2 (P25) NP bi-layer photoanode (NP/NP), sensitized with EY, showed an overall power conversion efficiency (η) of 0.89% under the illumination of 100 mW cm–2 (AM 1.5) with iodide-based liquid electrolyte. Whereas DSSCs fabricated with triple layered photoanode (NP/NF/NP) with the same total thickness and sensitized with EY yielded 1.77% efficiency under the same illumination conditions, showing an impressive ~99% enhancement in the overall power conversion efficiency. The DSSCs fabricated with RB-sensitized NP/NP and NP/NF/NP photoanodes showed 0.25 and 0.73% efficiencies, respectively. Upon optimization, DSSCs fabricated with co-sensitized NP/NP bi-layer and NP/NF/NP triple layer photoanodes showed 1.04 and 2.09% efficiencies, respectively, showing again an impressive ~100% enhancement in η due to the co-sensitized triple layer photoanode structure. Increase in the short circuit photocurrent density, UV–visible absorptions measurements, incident photon to current efficiency and electrochemical impedance spectroscopic measurements confirmed that this enhancement is very likely due to the enhanced light harvesting and reduction of recombination of photoelectrons combined with the enhanced spectral responses of the co-sensitized triple layered photoanode.</p

Efficiency enhancement of low-cost metal free dye sensitized solar cells via non-thermal atmospheric pressure plasma surface treatment

Dye sensitized solar cells (DSSC) are an attractive third-generation photovoltaic technology particularly promising for operation under diffuse and lower light conditions. However, high costs of the precious metals used for sensitizing dyes and low charge generation capability parameters limit the utility of DSSCs in comparison to conventional silicon solar cells. In this study, tin oxide (SnO2) photoelectrodes are treated with non-thermal atmospheric pressure plasmas to enhance photovoltaic performance. The effects of nitrogen and argon plasma surface treatment of photoanodes on the efficiency enhancement of DSSCs are systematically investigated by fabricating solar cells using pristine SnO2 and plasma-treated photoanodes. Solar cells made with Eosin Y sensitized pristine SnO2 photoanode exhibited a short circuit current density (JSC) of 1.03 mA cm−2 and an overall power conversion efficiency (PCE) of 0.30% whereas solar cells made with nitrogen plasma treated photoanode exhibited a JSC of 6.20 mA cm−2 and an overall PCE of 1.53% (4 times enhancement) under the same illumination of 100 mW cm−2 (AM 1.5). The efficiency of the solar cells fabricated with Ar plasma treated SnO2 photoanodes also showed an enhanced power conversion efficiency. Further characterizations revealed that the surface plasma treatments increased the surface roughness of the photoanodes. Plasma treatment led to the incorporation of nitrogen species and removal of surface impurities resulting in an increase in dye adsorption in the photoanode and hence the enhancement in the efficiency of the DSSC. This study demonstrated a one-pot treatment method for efficiency enhancement which could be used in various applications such as photovoltaic, catalytic and energy generation applications including DSSCs, thin-film solar cells, perovskite solar cells, gas sensing, bio-sensing, supercapacitors, Li-ion batteries and others.</p

High-efficiency dye-sensitized solar cells fabricated with electrospun PVdF-HFP polymer nanofibre-based gel electrolytes

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) electrospun polymer nanofibre-based quasi-solid or gel electrolytes were successfully fabricated by incorporating a liquid electrolyte within the nanofibre membrane. The dye-sensitized solar cells (DSSCs) fabricated with gel and with liquid electrolyte were characterized by photocurrent–voltage measurements and electrochemical impedance spectroscopy measurements. The maximum efficiency (η) of 6.79% was observed for the DSSC fabricated with optimized nanofibre membrane thickness, corresponding to 4 min of electrospinning time. The optimized PVdF-HFP nanofibre gel electrolyte shows an ionic conductivity of 7.16\ua0 7\ua010−3\ua0S cm–1 at 25\ub0C, while the corresponding liquid electrolyte exhibits an ionic conductivity of 11.69\ua0 7\ua010–3\ua0S cm–1 at the same temperature. The open circuit voltage (Voc), short circuit current density (Jsc) and fill factor were recorded as 801.40\ua0mV, 12.70\ua0mA\ua0cm–2, and 66.67%, respectively, at an incident light intensity of 100\ua0mW\ua0cm–2 with a 1.5\ua0AM filter. The nanofibre gel electrolyte-based cell showed an efficiency of 6.79%, whereas the efficiency of the conventional liquid electrolyte-based cell was 7.28% under the same conditions. Furthermore, nanofibre gel electrolyte-based cells exhibited better stability, maintaining 85.40% of initial efficiency after 120\ua0h. These results show that the optimized, polymer nanofibre-based gel electrolyte can be used successfully to replace the liquid electrolyte in DSSCs without much loss of efficiency but improving the stability while minimizing most of the drawbacks associated with liquid electrolytes