Conductive Oxide-less Dye-sensitized Solar Cells Research Articles

Characteristics of Sputtered Cr Thin Films and Application as a Working Electrode in Transparent Conductive Oxide-Less Dye-Sensitized Solar Cells.

Cr metal electrode was suggested as the working electrode material to fabricate DSSCs without the TCO, and thin films were fabricated by an unbalanced magnetron sputtering system. The surface morphologies show uniform and smooth surfaces regardless of various film thicknesses, and the small crystallites of various sizes were showed with the vertical direction on the surface of Cr thin films with the increase of film thickness. And also, the root mean square (RMS) surface roughness value of Cr thin films increased, and the sheet resistance is decreased with the increase of film thickness. The maximum cell efficiency of the TCO-less DSSC was observed when a Cr working electrode with a thickness of 80 nm was applied to the TCO-less DSSC. Consequently, these results are related to the result of the optimization of conduction characteristics, transmission properties and surface properties of Cr thin films.

Transparent Conductive Oxide-Less Dye-Sensitized Solar Cells Consisting of Dye-Cocktail and Cobalt Based Redox Electrolyte

Thin Ti-metal protected stainless steel metal mesh coated with mesoporous TiO2 as flexible photoanode has been used to fabricate back contact transparent conductive oxide-less dye-sensitized solar cells. TiO2 nanoparticle having a particle size of 15–20 nm sensitized with dye cocktail of two indoline dyes D-205 and D-131 were first utilized owing to their complementary light harvesting properties. Short-circuit photocurrent density (Jsc) for the dye cocktail combination of D-205 and D-131 (1:1) was found to be increased due to the increased photon harvesting in the 400–500 nm mainly associated with the contribution from D-131 dye. In addition, the electron recombination was suppressed when dye cocktail was employed as confirmed by the dark current measurement leading to higher open-circuit voltage (Voc). The enhanced Jsc accompanied with increased Voc resulted in to an improved efficiency of 3.59% for this cocktail combination. To enhance the efficiency even further, we have utilized TiO2 nanoparticle having a larger particle size of 30 nm facilitating the mass transport of the bulky [Co(bpy)3]3+/2+ redox species. In order to enhance the photon harvesting window TiO2 nanoparticles were sensitized with porphyrin dye (YD2-o-C8) along with different dye cocktail combinations with another complementary dye (Y123). Utilization of a dye cocktail of YD2-o-C8 and Y123 (4:1) led to improved photoconversion efficiency of 5.25% under simulated solar irradiation.

Transparent conductive oxide-less back contact dye-sensitized solar cells using flat titanium sheet with microholes for photoanode fabrication

A flat titanium sheet with microholes (FTS-MH) has been utilized to fabricate transparent conductive oxide-less dye-sensitized solar cells (TCO-less DSSCs) in back contact device architecture. Utilization of FTS-MH to fabricate a TCO-less photoanode offers several advantages in terms of simplicity and ease of fabrication as compared with the TCO-less DSSCs structure reported previously. Hydrogen peroxide (H2O2) surface treatments on FTS-MH have shown important factors to enhance the photoanode properties. H2O2 surface treatment is able to change the surface morphology of FTS-MH, and the created anatase titanium dioxide (TiO2) nanostructures increase the surface contact between the FTS-MH and the coated mesoporous TiO2. Electrochemical impedance investigations reveled that improvements of the FTS-MH/TiO2 and TiO2/dye/electrolyte interface led to hampered charge recombination resulting in enhancement of both short-circuit current density and open-circuit voltage, respectively. Even after removal of both TCO layers, our complete TCO-less DSSCs exhibited a power conversion efficiency of 7.25% under simulated solar irradiation.

Transparent conductive oxide-less dye-sensitized solar cells (TCO-less DSSC) with titanium nitride compact layer on back contact Ti metal mesh

Transparent conductive oxide-less dye-sensitized solar cells with back contact Ti electrodes covered by thin compact titanium nitride (TiN) layer were studied. The TiN compact layer was fabricated on the surface of Ti wire by exposing Ti wires to laser under nitrogen atmosphere. The photovoltaic performance was improved after the compact TiN blocking layer was fabricated on the Ti wire. These results were explained by the suppression of charge recombination between electrons in Ti wires and I3- in electrolytes by the TiN compact layer.

Effect of Substrate Temperature on Ti/TiO2 Layers Growth Using a Combined Sputtering/Sol-Gel Combustion Method.

A combined radio frequency sputtering/sol-gel combustion method was investigated in order to obtain optimum process condition for fabrication of a Titanium (Ti)/Titanium oxide (TiO2) films electrode of transparent conductive oxide-less dye-sensitized solar cells (TCO-less DSCs), Experimentally, the substrate temperature was changed from R.T. to 500 °C, and it was found that there existed an optimum value for efficient performance of the cell. The porous Ti layer with low sheet resistance (-2.5 Ω/sq.) can be prepared by substrate temperature 250 °C under RF power 300 W and Ar 8 mTorr. The efficiency (η) of the cell was 6.52% [FF: 0.76, VOC: 0.72 V, JSC: 11.91 mA/cm2].

Preparation of double layer porous films of Titanium/Titanium oxide for photoelectrochemical cells application

Double layer nanoporous films of Titanium (Ti)/Titanium oxide (TiO2) were fabricated by a combined radio frequency sputtering and sol–gel combustion method and investigated with respect to its photo-anode properties of transparent conductive oxide-less dye-sensitized solar cells (TCO-less DSCs). The porous Ti layer can collect electrons from the TiO2 layer and allows the ionic diffusion of iodide ion/triiodide ion (I-/I3-) through the hole. The porous Ti layer with low sheet resistance (∼2.7Ω/sq.) can be prepared by substrate temperature 300°C under RF power 300W and Ar gas pressure 5mTorr. The Ti/TiO2 double layers prepared by combined RFS/SGC method show the good impedance characteristics. The efficiency (η) of prepared TCO-less DSCs sample is 5.73% [fill factor (ff): 0.76, open circuit voltage (Voc): 0.71V, short-circuit current density (Jsc): 10.61mA/cm2].

Preparation of Nanoporous Ti/TiO2 Layers Deposition by RF-magnetron Sputtering/Sol-Gel Combustion Procedure for Dye-sensitized Solar Cell

Nanoporous Titanium (Ti) / Titanium oxide (TiO2) film electrodes were fabricated by a combined radio frequency-sputtering (RFS) / Sol-gel combustion (SGC) method and investigated with respect to its photo-anode properties of transparent conductive oxide-less dye-sensitized solar cells (TCO-less DSCs). The porous Ti layer can collect electrons from the TiO2 layer and allows the ionic diffusion of I-/I3− through the hole. The porous Ti layer with low sheet resistance (∼1.7Ω/sq.) can be prepared by substrate temperature 250oC under RF power 300W and Ar gas pressure 8 mTorr. The Ti/TiO2 layers prepared by combined RFS/SGC method show the good impedance characteristics. The efficiency (η) of prepared TCO-less DSCs sample is 5.73% [fill factor (ff): 0.76, open circuit voltage (Voc): 0.71V, short-circuit current density (Jsc): 10.61mA/cm2].

Fabrication of transparent conductive oxide-less dye-sensitized solar cells consisting of Ti electrodes by electron-beam evaporation process

In this paper, we report a fabrication process of transparent conductive oxide (TCO)-less dye-sensitized solar cell. In the proposed cell fabrication process, TCO electrode is replaced with Ti electrode. Ti layer is deposited by electron beam evaporation method on the backside of the printed TiO 2 layer. Due to the relatively rough surface of TiO 2 printing layer, deposited Ti electrode has porosity. This enables passing of the dye and electrolyte through the electrode. The proposed method has potential to achieve cost-effective manufacturing. The conversion efficiency is improved with increasing deposition time of Ti electrode, which suggests that the sheet resistance of the Ti electrode is one of the most important factors for improving solar cell performances in the proposed cell structure.