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Dyeing for Solar Power

Massey University researchers Dr David Officer and Dr Tony Burrell are using "man-made chlorophyll" in the form of groups of porphyrin molecules to develop a new form of solar cell. While individual porphyrin molecules have been used in solar cells in the past, the Massey team has been able to link them to form larger, more efficient energy-converting groups.

While natural porphyrin arrays are huge -- up to 300 linked at a time. The Massey team is building arrays of up to 33; the largest man-made arrays known. They have also improved the process for making the arrays, joining molecules in just a few steps, compared to up to 30 steps previously used.

Conventional solar cells are made from silicon, which is expensive, making solar more costly than other energy forms. At the beginning of the 1990s, Professor Michael Graetze, at the Swiss Federal Institute of Technology, developed titanium dioxide solar cells. These are made up of a light-harvesting material, a dye, on a thin layer of titanium dioxide sandwiched between conducting glass.

When the dye is struck by light, electrons are knocked free and are collected by the titanium dioxide, creating an electric current. The porphyrin arrays could be used as the dye in this process. These layers are so thin they are transparent, so could be integrated into a product, such as a digital watch face, and be both the power supply and display.

Titanium dioxide cells have an energy efficiency of 12%, similar to silicon cells. The use of better dyes such as porphyrins could provide efficiencies of greater than 30%, and would cost under US60c a watt, compared to the US$5 of current solar technology.