Researchers at Purdue University, Indiana, USA have created artificial photosystems using optical nanomaterials to harvest solar energy that is converted to solar power. The creation of a new type of solar cell that self-repairs using carbon nanotubes and DNA is hoped to be able to increase the life of the solar cell and reduce the cost of its production to make solar cells more affordable. The design uses the single-wall carbon nanotubes in the light harvesting cells' structure as molecular wires and uses molecular recognition and thermo-dynamic metastability (the ability for a system to be continuously dissolved and reassembled) to mimic nature's self repair system of natural photosynthetic systems in plants. The researchers' concept uses carbon nanotubes anchor strands of DNA which are engineered to have specific sequences of building blocks (nucleotides) and which allow them to recognise and attach to the solar cell's chromophores (the cell's light-absorbing dyes). As the DNA recognises the chromophores, the system spontaneously reassembles; in conventional cells the chlorophyll-like molecules of chromophores degrade when exposed to sunlight. When the chromophores are ready to be replaced, they can be removed either by the chemical process or by adding new DNA strands with different nucleotide sequences which remove the damaged molecules and then new chromophores will be added. The researchers, based at at Birck Nanontechnolgy and Bindley Bioscience centres at the university believe the concept could create a photoelectromechancial cell that operates at full capacity indefinitely, as long as there is a supply of chromophores. The research team is looking at synthetic chromophores instead of natural ones which have to be harvested and isolated from bacteria, which increases the cost of solar cell reproduction. Instead, researchers are investing synthetic chromophores made of synthetic dyes, or porphyrins.
