Dye-sensitized solar cells are photoelectrochemical cells that use photo-sensitization of wide-band-gap mesoporous oxide semiconductors. These cells were invented by Michael Graetzel et al.1) in 1991 and are also known as Graetzel cells. These cells are extremely promising because they are made of low-cost materials and do not need any big apparatus to manufacture. The cells have a simple structure that consists of two electrodes and an iodide-containing electrolyte. One electrode is dye-absorbed highly porous nanocrystalline titanium oxide (nc-TiO2) deposited on a transparent electrically conducting substrate. The other is a transparent electrically conducting substrate only. The cells have been compared to photosynthesis because they use the redox reaction of the electrolyte. The energy conversion efficiency of the cells has not yet reached the level of silicon solar cells. The current energy conversion efficiency is about 10%, as was reported by Graetzel et al. It is thought that the energy conversion efficiency can rise to 33% in theory. == Principle == Solar light passes through an electrically conductive glass electrode, and dyes adsorbed to the electrode are irradiated. When a dye absorbs solar light, one of the electrons in the dye transits from a ground state to an excited state. This phenomenon is called photoexcitation. The excited electron makes a jump from the dye to the conduction band in TiO2.This jump occurs very rapidly; it takes only 10-15 seconds. In TiO2, the electron diffuses across the TiO2 film, reaches the glass electrode, goes through conducting wire, and reaches the counter electrode. After the electron makes the jump from the dye to TiO2, the dye changes into an oxidation state. In order to restore the dye, an iodide ion gives one electron to the dye and becomes iodine. This iodine diffuses to the counter electrode, receives one electron, and become an iodide ion again. This is how a dye-sensitized solar cell receives solar energy and gives electric current to an external circuit. == Reference == 1)Brian O'Regan & Michael Graetzel, ''Nature,'' 353 (24), 737 (1991).
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Dye-sensitized solar cells
Dye-sensitized solar cells are photoelectrochemical cells that use photo-sensitization of wide-band-gap mesoporous oxide semiconductors. These cells were invented by Michael Graetzel et al.1) in 1991 and are also known as Graetzel cells. These cells are extremely promising because they are made of low-cost materials and do not need any big apparatus to manufacture. The cells have a simple structure that consists of two electrodes and an iodide-containing electrolyte. One electrode is dye-absorbed highly porous nanocrystalline titanium oxide (nc-TiO2) deposited on a transparent electrically conducting substrate. The other is a transparent electrically conducting substrate only. The cells have been compared to photosynthesis because they use the redox reaction of the electrolyte. The energy conversion efficiency of the cells has not yet reached the level of silicon solar cells. The current energy conversion efficiency is about 10%, as was reported by Graetzel et al. It is thought that the energy conversion efficiency can rise to 33% in theory. == Principle == Solar light passes through an electrically conductive glass electrode, and dyes adsorbed to the electrode are irradiated. When a dye absorbs solar light, one of the electrons in the dye transits from a ground state to an excited state. This phenomenon is called photoexcitation. The excited electron makes a jump from the dye to the conduction band in TiO2.This jump occurs very rapidly; it takes only 10-15 seconds. In TiO2, the electron diffuses across the TiO2 film, reaches the glass electrode, goes through conducting wire, and reaches the counter electrode. After the electron makes the jump from the dye to TiO2, the dye changes into an oxidation state. In order to restore the dye, an iodide ion gives one electron to the dye and becomes iodine. This iodine diffuses to the counter electrode, receives one electron, and become an iodide ion again. This is how a dye-sensitized solar cell receives solar energy and gives electric current to an external circuit. == Reference == 1)Brian O'Regan & Michael Graetzel, ''Nature,'' 353 (24), 737 (1991).
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