PV Watch

A couple of interesting developments may eventually have a big positive impact on the efficiency of photovoltaic cells. Last month, MIT researchers reported at a meeting of the Materials Research Society that they had found generic methods of boosting the efficiency of a PV cell by as much as 50 percent. The dozen or so researchers led by Lionel Kimerling did thousands of computer simulations to figure out how a cellâ''s performance could best be improved by combinations of anti-reflective coatings and diffraction gratings, and then validated their results with lab tests.

Meanwhile, scientists led by the distinguished chemist Malcolm Chisholm of Ohio State University have doped a polymer commonly used in semiconductor applications to produce a PV material that responds to light in wavelengths from ultraviolet to infrared. Typical silicon cells function well only in a much narrower range, from orange to deep red.

Freelancer Jesse Emspak or one of his editors at Scientific American deserve credit, assuming they have it right, for spotting the Chisholm story and (apparently) grasping its significance. The title of the PNAS article reporting the doped polymer reads: â''The remarkable influence of M2ο to thienyl Ï' conjugation in oligothiophenes incorporating MM quadruple bonds.â'' Just as invitingly, the first sentence of the abstract says, â''Oligothiophenes incorporating MM quadruple bonds have been prepared from the reactions between Mo2(TiPB)4 (TiPB = 2,4,6-triisopropyl benzoate) and 3â'²,4â'²-dihexyl-2,2â'²-:5â'²,2â'³-terthiophene-5,5â'³-dicarboxylic acid.â''

In yet another innovative approach to improving the light yield in solar cells, researchers at the FOM Institute for Atomic and Molecular Physics in The Netherlands suggest lacing thin-film PV material with nanoscopic metal particles. These generate surface plasmon waves when hit by light, and if the particles are sized and arranged just right, light is scattered more thoroughly and the harvest of light can be improved at wavelengths that otherwise are poorly captured.

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