Impedance Of Dye-sensitized Solar Cell Research Articles

Electron Conduction Channel of Silver Nanowire Modified TiO₂ Photoanode for Improvement of Interface Impedance of Dye-Sensitized Solar Cell

In this article, novel double-layer films were designed and examined for dye-sensitized solar cells (DSSCs). The commercial titanium dioxide (TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) nanoparticles as a bonding underlayer, and the silver nanowires (AgNWs) were used and prepared by means of the polyol method. They which were doped into TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> composite materials. The microstructure of AgNWs and the effect of modified DSSCs on photovoltaic (PV) performance were examined. The experimental research indicated that the localized surface plasmon resonance (LSPR) could enhance light-harvesting efficiency. The exceptional electrical conductivity of silver nanowires also improved the interface resistance of DSSCs. We found that LSPR could substantially boost the incident photon-to-electron conversion efficiency (IPCE) of such DSSCs. The AgNWs@TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (an optimized content of 3 wt% in photoanode) improved the photovoltaic conversion efficiency (η) of the DSSCs from 4.01% to 5.88%, when compared with the DSSCs without AgNWs@TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (pure TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ).

Properties of Dye Sensitized Solar Cells with Adding Nano Carbon Black into Blocking Layer

Blocking layers with nano carbon blacks (NCBs) were prepared by adding 0.0 ~ 0.5 wt% NCBs to the TiO₂ blocking layer. Then, dye sensitized solar cells (DSSCs) were fabricated with a 0.45 ㎠ active area. TEM and micro-Raman spectroscopy were used to characterize the microstructure and phases of the NCBs, respectively. Optical microscopy and AFM were used to analyze the microstructure of the TiO₂ blocking layer with NCBs. UV-VIS-NIS spectroscopy was used to determine the band gap of the TiO₂ blocking layer with NCBs. A solar simulator and potentiostat were used to determine the photovoltaic properties and impedance of DSSCs with NCBs. The energy conversion efficiency (ECE) increased from 3.53 to 6.20 % when the NCB content increased from 0.0 to 0.3 wt%. This indicates that the effective surface area and electron mobility increased in the TiO₂ blocking layer with NCBs. However, the ECE decreased when the NCB content was increased to over 0.4 wt%. This change occurred because the effective electron transport area decreased with the addition of excessive NCBs to the TiO₂ blocking layer. The results of this study suggest that the ECE of DSSCs can be enhanced by adding the appropriate amount of NCBs to the TiO₂ blocking layer.

Modeling of the dye loading time influence on the electrical impedance of a dye-sensitized solar cell

A hemisquaraine dye molecule (CT1) was used as TiO2 sensitizer. The influence of the dye-adsorption time on the electrical impedance of a CT1-based dye-sensitized solar cell (DSC) was analyzed. Differently from what we observed with commercial Ru dye-based DSC, a non-monotonic effect of the impregnation time on the impedance has been found and the dye loading time is much reduced, a desirable outcome in economic grounds. This feature is analyzed in terms of the dye molecules tendency to aggregate close to the TiO2/electrolyte interface. A physical model that fits well the experimental data is proposed, which also takes into account a correction related to the difference between the illuminated area of the cell and the total area available in the electrical measurements.

Faradaic impedance of dye-sensitized solar cells

Theoretical equations of the Faradaic impedance of the photoelectrode and the counter electrode of dye-sensitized solar cell (DSC) were derived. The Faradaic impedance is the frequency dependent resistance related to the time constants of elementary electrode processes like photoexcitation, electron transfer, charge transfer reaction and diffusion. The typical cell impedance spectrum describes the locus of three semicircles on the Nyquist plane. The locus of three semicircles is generally analyzed by using the equivalent circuit composed of charge transfer resistance ( R ct,1) and capacitance ( C dl,1) of counter electrode, charge transfer resistance ( R ct,2) and capacitance ( C dl,2) of photoelectrode, the finite diffusion impedance due to the diffusion of I 3 − on the counter electrode ( Z w), and total resistance of the substrate and solution ( R s). The physical meanings of R ct,1 and R ct,2 can be elucidated by the interpretations of Faradaic impedance derived in the present paper. The R ct,1 is represented as the function of the potential-dependent rate constants of I 3 − reduction and I − oxidation. On the other hand, the R ct,2 is the function of the photoelectrode potential, the surface concentration of I 3 − and the potential-independent rate constant of the back electron transfer reaction. The theoretical expressions of the current–voltage ( I– V) curve of the DSC can be also derived. In the present paper, the relations between the impedance and I– V curve of the DSC are discussed.

The analysis of the change in the performance and impedance of dye-sensitized solar cell according to the dye-adsorption time

Dye-sensitized solar cells (DSCs) have been expected to be an alternative to the conventional silicon solar cell because of its advantages such as simple fabrication process, low manufacturing costs, and various applications. The related researches have been conducted so far for the improvement of the efficiency. However, the adsorption process usually takes 24 h and it may actually be responsible for deteriorative overall productivity. Therefore, in this study, we tried to investigate the optimal dye-adsorption time by analyzing the photovoltaic performance and the electrochemical impedance. If the adsorption time was insufficient, it was not enough for dye to adsorb on TiO 2. And the current was increased with the increase in the adsorption time. However, the increase stopped after dye molecules covered with whole TiO 2 surface. DSCs were fabricated under identical condition except for the adsorption time from 1 to 24 h. The change in the outputs of DSCs was verified by the I– V characteristic curves and the electrochemical impedance spectroscopy. As a result, the output was proportion to the adsorption time before sufficient adsorption and the performance was saturated after that. The irradiated area was 0.25 cm 2 and the maximum efficiency was 6.98%.

Analyses of the output characteristics and the change of internal impedance of Dye-sensitized solar cell according to the adsorption time

Dye-sensitized solar cell (DSC) has been expected to be an alternative to the conventional silicon solar cell due to simple manufacturing process and low fabrication casts. In order to improve productivity of DSC, we attempted to optimize the required time of the adsorption process. According to the change in the adsorption time from 1 to 24h, We analyzed the output characteristics and the change of internal impedance. As a result, The outputs of DSC were continuously increased until 12h of the adsorption time and remained the same after that. Also, We reconfirmed this result that 12h was optimum adsorption by the analysis of the electrochemical impedance spectroscope because the internal impedance was similar to the output.

Electrochemical Impedance of Dye-Sensitized Solar Cells

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