The Use of Nanostructured Calcium Silicate in Solar Cells

<p>Nanostructured calcium silicate (NCaSil) had previously been found to be photoactive and mildly semiconducting. Its use in solar cells was investigated in this project. Many different types of solar cells exist. Most common on the market are silicon-based cells, which generate charge separation through electric fields at p/n junctions. Over the last decade, dye-sensitised solar cells (DSSCs) have been heavily researched. DSSCs depend on effective electron/hole separation at the dye and efficient transfer to the electron- and hole-conducting materials. An older and little-researched form of cells is the photogalvanic cell, of which there are two forms. One contains a semiconducting material, whereas the other comprises of either one or two redox couples, in which at least one species is photoactive. An example of the latter form of cell is the odide/triiodide redox couple, which is commonly the electrolyte of choice in DSSCs and semiconductor-containing photogalvanic cells. This project predominantly investigated the use of NCaSil in conjunction with the iodide/triiodide redox couple and its use in solar cells. The project ascertained that, when used with the iodide/triiodide, the NCaSil did not act as a semiconducting material (either as in a DSSC or semiconductor photogalvanic cell). Rather iodide/triiodide's photogalvanic process dominated the cell, despite the presence of NCaSil. Furthermore, the addition of the stable NCaSils to the iodide/triiodide (with 5 wt% CaCl2) created "soggy sand electrolytes". These electrolytes showed increased conductivities, despite their higher viscosities, due to a synergistic effect. Soggy sand electrolytes show great promise in the development of more solid-like DSSCs. Furthermore, the project observed that the performance of NCaSil cells was maximized with a 70 wt% ethanol (30 wt% water) solvated electrolyte, with 1.5 wt% CaCl2 added to this electrolyte (or 5 wt % CaCl2 in the water content). When used long-term in conjunction with Reinforced NCaSil, a gel was formed, which showed promising activity. This activity was attributed to the interaction of surface-bound Ca2+ to iodine. Similar gels formed from vanadium- and cerium-treated NCaSil also showed great cell performance. Cell performance was further enhanced by backing the cell with a reflective or light scattering material, such as Teflon tape.</p>

The Use of Nanostructured Calcium Silicate in Solar Cells

<p>Nanostructured calcium silicate (NCaSil) had previously been found to be photoactive and mildly semiconducting. Its use in solar cells was investigated in this project. Many different types of solar cells exist. Most common on the market are silicon-based cells, which generate charge separation through electric fields at p/n junctions. Over the last decade, dye-sensitised solar cells (DSSCs) have been heavily researched. DSSCs depend on effective electron/hole separation at the dye and efficient transfer to the electron- and hole-conducting materials. An older and little-researched form of cells is the photogalvanic cell, of which there are two forms. One contains a semiconducting material, whereas the other comprises of either one or two redox couples, in which at least one species is photoactive. An example of the latter form of cell is the odide/triiodide redox couple, which is commonly the electrolyte of choice in DSSCs and semiconductor-containing photogalvanic cells. This project predominantly investigated the use of NCaSil in conjunction with the iodide/triiodide redox couple and its use in solar cells. The project ascertained that, when used with the iodide/triiodide, the NCaSil did not act as a semiconducting material (either as in a DSSC or semiconductor photogalvanic cell). Rather iodide/triiodide's photogalvanic process dominated the cell, despite the presence of NCaSil. Furthermore, the addition of the stable NCaSils to the iodide/triiodide (with 5 wt% CaCl2) created "soggy sand electrolytes". These electrolytes showed increased conductivities, despite their higher viscosities, due to a synergistic effect. Soggy sand electrolytes show great promise in the development of more solid-like DSSCs. Furthermore, the project observed that the performance of NCaSil cells was maximized with a 70 wt% ethanol (30 wt% water) solvated electrolyte, with 1.5 wt% CaCl2 added to this electrolyte (or 5 wt % CaCl2 in the water content). When used long-term in conjunction with Reinforced NCaSil, a gel was formed, which showed promising activity. This activity was attributed to the interaction of surface-bound Ca2+ to iodine. Similar gels formed from vanadium- and cerium-treated NCaSil also showed great cell performance. Cell performance was further enhanced by backing the cell with a reflective or light scattering material, such as Teflon tape.</p>

Enhancement of Photogalvanic Effect of Toluidine Blue Dye using Sodium Lauryl Sulphate as an Efficient Additive for Solar Energy Conversion and Storage

In photogalvanic cells, electron transfer reactions can lead to the inexpensive production of solar power with an inherent storage capacity because in solution, the ions involved act as mobile charges through diffusion. This study improved the storage capacity and solar power of photogalvanic cells comprising ethylenediamine acetic acid (EDTA), toluidine blue and sodium lauryl sulphate (NaLS) as a reductant, photosensitizer and surfactant, respectively. The observed maximum photocurrent, photopotential, and open circuit voltage, of the photogalvanic cell were 150 A, 743 mV and 1065 mV, respectively. The efficiency of conversion cells was approximately 0.2630%. In the dark, the storage capacity (t0.5) was 124 min for the photogalvanic cell. The optimization of the influence of different parameters such as variation in photosensitizer concentration, surfactant, reductant, pH, and temperature as well as the electrical output was performed. A mechanism was proposed for photocurrent generation in the photogalvanic cell.

Enhanced Efficiency of Photogalvanic Cell based on Mixed Triphenylmethane Dyes

The study focused on the enhancement of solar power generation and storage capacity of a photogalvanic cell ethylene diaminetetraacetic acid as reductant, xylene cyanol FF and patent blue as photosensitizers. This chemical system with changed concentrations, a combination electrode and a very small Pt electrode was used to fabricate a modified photogalvanic cell. The modified cell showed greatly enhanced performance in terms of photopotential (868.0 mV), photocurrent (230.0 μA), efficiency (0.64 %) and the maximum output (power) of the cell was found to be 199.64 W. The photogalvanic cell can be used at this power level for 115 min in the dark due to the storage capacity of the cell. The effects of various parameters such as pH, reductant concentration, dye concentration, diffusion length, light intensity, and electrode area on electrical output of the cell were also investigated. The current-voltage (i-v) characteristics of the cell have been studied and a mechanism for the photocurrent generation in photogalvanic cell has also been proposed.

Utilization of Mixed Naphthol Green B and Janus Green B Dyes as Photosensitier in Photogalvanic Cell for Solar Energy Conversion and Storage

In this work, a new dye-sensitized solar cell (DSSC) was prepared using naphthol green B and Janus green B as photosensitizers and EDTA as reductant. A 210 μA of photocurrent and 1018 mV of photo-potential were generated using these dyes. The fill factor of 0.40, a conversion efficiency was observed to be 1.0028% and the power or maximum output of cell was calculated to be 213.78 μW. Because of the storage capacity in a cell, a DSSC can be used for a total of 180 min in dark. The properties of mixed photosensitize system EDTA-NGB-JGB were characterized and evaluated by UV-visible, fluorosencemeter, FESEM and XRD analysis. The photocurrent generation mechanism in photogalvanic cell was also discussed