Minna Toivola

Review of materials and manufacturing options for large area flexible dye solar cells

This review covers the current state of the art related to up-scaling and commercialization of dye solar cells (DSC). The cost analysis of the different components and manufacturing of DSC gives an estimate on the overall production costs. Moreover, it provides an insight in which areas improvement is needed in order to reach significant cost reductions. As a result of the cost analysis, transferring the technology to flexible substrates and employment of simple roll-to-roll production methods were found the key issues. The focus of this work was set accordingly. In this work, appropriate materials along with their unique fabrication processes and different design methods are investigated highlighting their advantages and limitations. The basic goal is to identify the best materials and preparation techniques suitable for an ideal roll-to-roll process of flexible dye solar module fabrication as well as the areas where further development is still needed.

Dye Solar Cells on ITO-PET Substrate with TiO2 Recombination Blocking Layers

Atomic-layer-deposited TiO 2 recombination blocking layers were prepared on indium tin oxide-poly(ethylene terephthalate) (ITO-PET) photoelectrode substrates for dye solar cells and were examined using several electrochemical methods. The blocking layers increased the open-circuit voltage at low light intensities. At high light intensities, a decrease in the fill factor (FF) due to the additional resistance of the current transport through the layer was more significant than the positive effect by the reduced recombination. The decrease in the FF was reduced by a thermal treatment that made the blocking layer more conductive due to a structural change from an amorphous to a crystalline form. Therefore, thinner blocking layers of this type are required for plastic cells prepared at low temperature than for conventional glass dye solar cells made with temperature processing.

Stability of Dye Solar Cells with Photoelectrode on Metal Substrates

In this study, the stability of dye solar cells DSCs with different kinds of metals as the photoelectrode substrate is studied.Stainless steels StSs, Inconel, and titanium substrates were tested to find stable substrate options. Photovoltaic characterization,electrochemical impedance spectroscopy EIS, scanning electron microscopy, and substrate polarization measurements were usedin the characterization. DSCs based on different grades of StS suffered from rapid degradation of efficiency within few hours inlight soaking. Good stability was demonstrated with DSCs with Inconel and Ti photoelectrode substrates. The Inconel substrateshave a thick passive oxide layer, which is likely related to good stability. However, according to the EIS analysis, the oxide layerof Inconel substrates increased resistive losses, which caused a lower fill factor and photovoltaic efficiency compared to theTi-based cells.© 2010 The Electrochemical Society. DOI: 10.1149/1.3374645 All rights reserved.Manuscript submitted December 17, 2009; revised manuscript received February 19, 2010. Published April 21, 2010.

Investigation of Temperature and Aging Effects in Nanostructured Dye Solar Cells Studied by Electrochemical Impedance Spectroscopy

Effects of aging and cyclically varying temperature on the electrical parameters of dye solar cells were analyzed with electrochemical impedance spectroscopy. Photoelectrode total resistance increased as a function of time due to increasing electron transport resistance in the film. On the other hand, photoelectrode recombination resistance was generally larger, electron lifetimes in the were film longer, and charge transfer resistance on the counter electrode was smaller after the temperature treatments than before them. These effects correlated with the slower deterioration rate of the temperature-treated cells, in comparison to the reference cells.

The performance enhanced by back reflection in nanostructured dye-sensitized solar cells

Dye-sensitized solar cell (DSSC) cannot absorb all the incident light, and some parts of light transits the cell and is unused. The work presented here dealt with transmitted light to enhance the performance by using the back reflection of stainless steel substrate. The influence of surface roughness of stainless steel substrate DSSC was investigated. Three kind of surface roughness were used in the DSSCs. The result showed that the I–V parameters were not sensitive to the surface properties of stainless steel. Some controlled surfaces of substrate were suggested in the further research. The influence of the thickness of TiO2 photoelectrode film was also researched. The optimal thickness of stainless steel DSSC was larger than glass substrate DSSC and over 30 µm.