The mechanism for converting solar energy into electrical energy in a dye-sensitised solar cell is a five-step process (see Fig 1). Solar energy ( h ,as photons of light) causes electrons in the molecular orbitals withinthe adsorbed dye sensitiser (S) molecules to become photoexcited(S*):
S(adsorbed on TiO2) + h  S*(adsorbed on TiO2) ( i) (Thetrapping of solar energy by a sensitiser molecule is analogous to thelight-absorbing chlorophyll molecule found in Nature, which convertscarbon dioxide and water to glucose and oxygen.) S*(adsorbed on TiO2) S+(adsorbed on TiO2) + e- ( ii) The free electrons then move through the conduction band of TiO2, gather at the anode (the dyed TiO2 plate), and then start to flow as an electric current through the external load to the counter electrode. The oxidised dye (S+)is reduced to the original form (S) by regaining electrons from theorganic electrolyte solution that contains the iodide/tri-iodide redoxsystem, with the iodide ions being oxidised (loss of electrons) totri-iodide ions:
S+(adsorbed on TiO2) + 3/2I- S(adsorbed on TiO2) + ½I3- ( iii) Torestore the iodide ions, free electrons at the counter (graphite)electrode (which have travelled around the circuit) reduce thetri-iodide molecules back to their iodide state. The dye molecules arethen ready for the next excitation/oxidation/reduction cycle.
Grätzel cells comprise two transparent conducting oxide glass plates sandwiched together ( Figs 2 and 3).Typically fluorine-doped indium oxide or tin-doped indium oxide areused. The thin oxide coating on one side of the glass makes the glasssurface electrically conducting. The upper plate (the 'photoanode'),has the sensitising dye adsorbed onto a 10  m layer of randomly-stacked nanoparticles ( ca 20 nm in diameter) of TiO2.
For research investigations, a thin film of platinum is chemicallydeposited onto the lower plate as a conductor and catalyst. However,for demonstrations, simply coating the lower plate with graphite from asoft pencil will suffice. The upper and lower plates are securedtogether with a paperclip 'clamp' (Fig 3). To finish the cell,a drop of organic electrolyte solution, which contains theiodide/tri-iodide redox couple, is applied between the plates.
To make the TiO2 plates a little time needs to be invested. Using a microscope slide, apply the TiO2 powder and paste mix as a colloidal suspension. Electronic contact between the TiO2particles is produced by sintering at 450 ºC (30 minutes in an oven orfurnace) or heating over a (blue flame) Bunsen burner. If you use aBunsen burner, the sintering process should not take more than threeminutes to complete. The white TiO2 coating will start tocolour brown after approximately one minute and then gradually turnwhite again. At this point, the sintering process is complete.Conductive glass slides and TiO2-coated conductive glassslides can be bought separately for additional solar cells or forschools which have access to the other kit components.
Various natural organic dyes can be adsorbed onto the TiO2 nanoparticles for use as the light-harvesting sensitiser molecule. The best natural dyes are the purple-red anthocyanins (1),found in blackberries, raspberries, beetroot, cranberries, cherries,hibiscus tea leaves, and blackcurrants. To extract the dye fromblackberries or raspberries, add four berries to a mortar with 20 cm3of warm water and crush the berries using a pestle. To prepare thehibiscus tea dye soak a few grams of the dried leaves in boiling waterfor a few minutes and decant the solution. Stain the TiO2 plates by immersing them into the dye solution for 10 minutes and then dry using a hair drier. The dyed TiO2plates are re-usable, the dye can be removed by leaving the plates to soak in water for a few hours. The process is enhanced under exposureto uv light, taking advantage of the photocatalytic properties of TiO2.
对不起找不到华文的。
问题是那里可以买到TiO2？
[ 本帖最后由 treetop 于 26-6-2008 09:42 AM 编辑 ] | 
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发表于 22-6-2008 04:20 PM
变色卡
千斤顶
楼主
就是啦！
发表于 20-7-2008 02:39 AM
他们要暗爽就由得他们吧
一个封闭系统的的能量不会改变。不同的能量形式之间可以相互转化，但是
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