Enhanced performance of flexible dye-sensitized solar cells: Electrodeposition of Mg (OH) 2 on a nanocrystalline TiO2 electrode

Nanocrystalline TiO2 photoanodes were prepared on a conductive indium–tin oxide coated polyethylene naphthalate (ITO-PEN) plastic substrate by the doctor-blade method to fabricate flexible dye-sensitized solar cells (DSCs). The surface of the photoanode was coated with Mg(OH)2 by electrodeposition and the deposition time was systematically varied (2, 4, 6, 8, and 10 min). Electrodeposited Mg(OH)2 was confirmed by IR and energy dispersive X-ray (EDX) analysis. The surface morphology was studied by scanning electron microscopy. The internal surface area of TiO2 was studied against the deposition time by taking into account the projected surface area of the photoelectrode and it shows that the internal surface area of the photoelectrode was reduced as the Mg(OH)2 deposition time increased. The performance of flexible DSCs on various deposition times of Mg(OH)2 was evaluated on the basis of their photocurrent density–voltage characteristics. Among the deposition times, 2 min showed the best performance in Voc on a treated flexible DSC, with resulting 847 mV and a photocurrent density of 7.13 mA/cm2, providing an overall light-to-electricity conversion efficiency of 4.01%. This photovoltage is among the highest attained for a flexible DSC to date. This notable increment in Voc at a thin layer of Mg(OH)2 was attributed to the suppression of recombination of photogenerated electrons via the exposed surface of ITO as well as TiO2 without influencing the internal surface area of the photoanode significantly

Preparation of nanocrystalline TiO2 electrodes for flexible dye-sensitized solar cells: influence of mechanical compression

Nanocrystalline TiO2 electrodes were prepared using binder-free TiO2 paste on conductive ITO-PEN substrates by the doctor-blade method at significantly low temperature (140 °C), and the electrodes were further processed under different compressions (10–60 MPa) in order to improve interparticle connections and adhesion between the nanoparticles and the ITO-PEN substrate. TiO2 electrodes compressed at 30 and 40 MPa had relatively less cracks with low crack width. Electrode compressed at 30 MPa showed the highest internal surface area. Electrode prepared at this compression showed the best dye-sensitized solar cell (DSC) performance with Voc of 805 mV, Jsc of 9.24 mA cm–2, and an overall efficiency of 4.39%. Electrochemical impedance spectroscopy (EIS) studies of the sandwiched cells employing bare nanocrystalline TiO2 electrode and Pt counter electrode in I–/I3– electrolyte showed that electrode compression significantly influences the stability of the cells. EIS data suggested that degradation/corrosion processes may take place on ITO-PEN for sandwiched cells made by TiO2 electrodes compressed at all pressures. Thirty and 40 MPa compressions showed a minor degradation of ITO. The recombination dynamics at the TiO2/electrolyte interface were influenced by the changes in the nanostructured electrode internal surface area, changes in electron transport properties (due to improved sintering), and possible degradation/corrosion of ITO-PEN. Open-circuit voltage decay (OCVD) measurements showed that the DSC made by the 30 MPa compressed TiO2 electrode had the highest decay time, indicating low recombination properties, which is in a good agreement with other data

Preparation of nanocrystalline TiO2 electrodes for flexible dye-sensitized solar cells: influence of mechanical compression

Nanocrystalline TiO2 electrodes were prepared using binder-free TiO2 paste on conductive ITO-PEN substrates by the doctor-blade method at significantly low temperature (140 °C), and the electrodes were further processed under different compressions (10–60 MPa) in order to improve interparticle connections and adhesion between the nanoparticles and the ITO-PEN substrate. TiO2 electrodes compressed at 30 and 40 MPa had relatively less cracks with low crack width. Electrode compressed at 30 MPa showed the highest internal surface area. Electrode prepared at this compression showed the best dye-sensitized solar cell (DSC) performance with Voc of 805 mV, Jsc of 9.24 mA cm–2, and an overall efficiency of 4.39%. Electrochemical impedance spectroscopy (EIS) studies of the sandwiched cells employing bare nanocrystalline TiO2 electrode and Pt counter electrode in I–/I3– electrolyte showed that electrode compression significantly influences the stability of the cells. EIS data suggested that degradation/corrosion processes may take place on ITO-PEN for sandwiched cells made by TiO2 electrodes compressed at all pressures. Thirty and 40 MPa compressions showed a minor degradation of ITO. The recombination dynamics at the TiO2/electrolyte interface were influenced by the changes in the nanostructured electrode internal surface area, changes in electron transport properties (due to improved sintering), and possible degradation/corrosion of ITO-PEN. Open-circuit voltage decay (OCVD) measurements showed that the DSC made by the 30 MPa compressed TiO2 electrode had the highest decay time, indicating low recombination properties, which is in a good agreement with other data

Aerosol-assisted CVD of bismuth vanadate thin films and their photoelectrochemical properties

Thin film bismuth vanadate (BiVO4) photoelectrodes are prepared by aerosol-assisted (AA)CVD for the first time on fluorine-doped tin oxide (FTO) glass substrates. The BiVO4 photoelectrodes are characterised by X-ray diffraction (XRD), Raman spectroscopy (RS), and energy-dispersive X-ray (EDX) spectroscopy and are found to consist of phase-pure monoclinic BiVO4. Scanning electron microscopy (SEM) analysis shows that the thin film is uniform with a porous structure, and consists of particles approximatively 75-125 nm in diameter. The photoelectrochemical (PEC) properties of the BiVO4 photoelectrodes are studied in aqueous 1 M Na2SO4 and show photocurrent densities of 0.4 mA cm-2, and a maximum incident-photon-to-electron conversion efficiency (IPCE) of 19% at 1.23 V vs. the reversible hydrogen electrode (RHE). BiVO4 photoelectrodes prepared by this method are thus highly promising for use in PEC water-splitting cells

Effect of ZnO seed layer thickness on hierarchical ZnO nanorod growth on flexible substrates for application in dye-sensitised solar cells

ZnO nanorod (NR) arrays are considered to be suitable for application in flexible photovoltaic devices due to the high surface-to-volume ratio provided by the one-dimensional nanostructure. Hierarchical ZnO NRs were grown on flexible ITO/PEN substrates by sputtering a compact ZnO seed layer followed by chemical bath deposition. The effect of ZnO NR growth with the variation of the seed layer thickness (50, 100, 300, 500 and 800 nm) was studied. It has been found that by varying the seed layer thickness, the individual rod diameter, density and alignment can be controlled. The SEM images confirmed that relatively thin seed layers give rise to more dense films, whereas thick seed layers result in less dense films. The applications of flexible ZnO NR electrodes were tested by employing them in dye-sensitised solar cells (DSSC). The performance of flexible DSSCs was evaluated by studying the key cell parameters. The effect of the seed layer thickness on DSSC performance was investigated. It has been found that the overall cell efficiency increased when the seed layer thickness was varied from 50 to 500 nm, whereas sharp decrease in efficiency was observed when the thickness was further increased to 800 nm. It was found that a seed layer thickness of 500 nm gave the highest overall efficiency of 0.38% and incident photon-to-electron conversion efficiency of 6.5%. As well as having good electrical properties, ZnO NR films grown on ITO/PEN by this method have excellent reproducibility, and NR growth is readily controllable. This shows that these films have a wide range of potential applications including flexible energy harvesting and electronic devices. © Springer Science+Business Media 2013

Effect of Electrochemically Deposited MgO Coating on Printable Perovskite Solar Cell Performance

Herein, we studied the effect of MgO coating thickness on the performance of printable perovskite solar cells (PSCs) by varying the electrodeposition time of Mg(OH)2 on the fluorine-doped tin oxide (FTO)/TiO2 electrode. Electrodeposited Mg(OH)2 in the electrode was confirmed by energy dispersive X-ray (EDX) analysis and scanning electron microscopic (SEM) images. The performance of printable PSC structures on different deposition times of Mg(OH)2 was evaluated on the basis of their photocurrent density-voltage characteristics. The overall results confirmed that the insulating MgO coating has an adverse effect on the photovoltaic performance of the solid state printable PSCs. However, a marginal improvement in the device efficiency was obtained for the device made with the 30 s electrodeposited TiO2 electrode. We believe that this undesirable effect on the photovoltaic performance of the printable PSCs is due to the higher coverage of TiO2 by the insulating MgO layer attained by the electrodeposition technique