We now report metal-free organic dyes having a new type of indoline structure, which exhibits high efficiencies in dye-sensitized solar cells. The solar energy to current conversion efficiencies with the new indoline dye was 6.51%. Under the same conditions, the N3 dye was 7.89% and the N719 dye was 8.26%. The new indoline dye was optimized for the amount of 4-tert-butyl pyridine in the electrolyte and cholic acid as a coadsorbent. Subsequently, the solar energy to current conversion efficiencies reached 8.00%. This value was the highest obtained efficiency for dye-sensitized solar cells based on metal-free organic dyes without an antireflection layer.

The dye-sensitized solar cell (DSC) [1,2] is an attractive candidate for a new renewable energy source because of the low-cost materials and the facile manufacturing used in its production. [3] This cell has been intensively studied in the last decade. The photovoltaic effect in a DSC originates at the interface between a redox electrolyte containing iodide and triiodide (I -/I 3 -) ions and a dye-derivatized mesoscopic TiO 2 electrode. For outdoor applications, ionic liquids containing I -and I 3 -ions are the medium of choice because of their high thermal stability, non-flammability, negligible vapor pressure, and low toxicity. [4] Since the diffusion of I -and I 3 -ions in ionic liquids is slow owing to their high viscosity, [5] a thin nanocrystalline TiO 2 film is required to reach a high conversion efficiency. In order to compensate for the lower optical depth of such thin, porous electrodes, a high-extinction-coefficient dye should be used. A similar strategy is applied to other types of viscous electrolytes [6] and organic hole conductors. [7] The present study reports, for the first time, on a DSC combining a high-extinction-coefficient organic sensitizer with an ionic-liquid electrolyte. An indoline dye was employed (referred to as D149 below, Fig. 1), [8] which has an extinction coefficient (68 700 mol -1 cm -1 at 526 nm) that is five times higher than that of the conventional high-efficiency Ru dye (N719, 13 900 mol -1 cm -1 at 541 nm) [9] and reaches 8 % conversion efficiency with a volatile organic electrolyte. A screen-printed double layer, consisting of a nanocrystalline TiO 2 film and a scattering layer, constitute the mesoporous working electrode that supports the organic sensitizer (Fig. 1b). Below, we scrutinize the effect of the film thickness of nanocrystalline TiO 2 films on the photovoltaic performance of ionic-liquid-and acetonitrile (AcCN)-based electrolytes.Results obtained under 100 % sun irradiation are shown in Figure 2. The open-circuit photovoltage (V OC , Fig. 2a) decreases for both the AcCN-and ionic-liquid-based electrolytes with increasing film thickness, due to augmentation of the surface area, which provides additional charge-recombination sites [10][11][12] and enhances the dark current. [13] Moreover, for thick films the outer TiO 2 particle layers do not contribute significantly to the photogeneration of conduction-band electrons, owing to the filtering of light by the dyed particles located close to the fluorinated tin oxide (FTO) glass. The sharing of photoinjected conduction-band electrons by these particles lowers their quasi-Fermi level and hence the V OC . In contrast to the V oc , the short-circuit photocurrent density (J SC ), fill factor (FF), and overall solar-energy-conversion efficiency (g) obtained with the two electrolytes are affected in a different way by the film thickness. For the AcCN solvent (Fig. 2b), J SC increases continuously with film thickness, reaching a plateau value of close to 20 mA cm -2 at 14 lm, while g reaches a maximum of 9 % at a thicknes...

An indoline dye (D205), the synthesis method of which is disclosed in this report, gave high-efficiency organic dye-sensitized solar cells (9.52%) using an anti-aggregation reagent (chenodeoxycholic acid).

TiO(2) nanotube arrays prepared by electrochemical anodization of Ti foils show impressive light to electricity conversion efficiency in the dye-sensitized solar cells (DSCs). The length of the TiO(2) nanotube arrays (5-14 microm) was controlled by varying the anodization time from 2 to 20 h. The influence of nanotube lengths on the photovoltaic performance of DSCs was investigated by impedance. A flexible DSC using TiO(2) nanotube arrays on a Ti foil as a working electrode and polyethylene naphthalate (ITO/PEN) as counterelectrode in combination with solvent-free ionic liquid electrolyte achieved 3.6% photovoltaic conversion efficiency under simulated AM 1.5 sunlight.

Electrodeposition of inorganic compound thin films in the presence of certain organic molecules results in self‐assembly of various hybrid thin films with new properties. Examples of new discoveries by the authors are reviewed, taking cathodic formation of a ZnO/dye hybrid as the leading example. Hybridization of eosinY leads to the formation of highly oriented porous crystalline ZnO as the consequence of dye loading. The hybrid formation is a highly complicated process involving complex chemistry of many molecular and ionic constituents. However, electrochemical analyses of the relevant phenomena indicate the possibility of reaching a comprehensive understanding of the mechanism, giving us the chance to further develop them into industrial technologies. The porous crystals are ideal for photoelectrodes in dye‐sensitized solar cells. As the process also permits the use of non‐heat‐resistant substrates, the technology can be applied for the development of colorful and light‐weight plastic solar cells.