Transformation of a liquid electrolyte to a gel inside dye sensitized solar cells for better stability and performance

A gel electrolyte based on a metal-organic framework (MOF), comprised of Al3+ and trimesic acid, was used in dye-sensitized solar cells. The electrolyte was gelated inside the solar cell to ensure the best interfacial connection between the TiO2 photoanode and electrolyte ingredients. The photovoltaic performance of the solar cells showed that the gel has a good ability to preserve the function of liquid electrolytes. By optimizing the ratio of MOF and liquid electrolyte, the current density was improved, which was due to the increase in the redox couple I-/I-3(-) content in the gel electrolyte. The open-circuit voltage was affected because of the change in the conduction band of TiO2 by the introduction of Al3+ ions and also because of electron recombination. Thus, a slightly higher efficiency was achieved using the gel electrolyte compared to the liquid electrolyte based cells. A superior stability was achieved with the MOF gel electrolyte under thermal stress at 60 degrees C for 250 h, while the efficiency of cells with liquid electrolyte deteriorated continuously under the same conditions. The drop in efficiency in the liquid electrolyte cells, was 24%, compared to only a 6% drop in the MOF gel electrolyte cells.