Researchers from the University of British Columbia and the University of North Carolina have reported that using halogens in a dye-sensitized solar cell can increase conversion efficiency by 25%.

A dye-sensitized solar cell consists of an electrolyte, two electrodes and a thin semiconductor film coated with a light-absorbing dye. When light strikes the dye, it releases electrons into the semiconductor and from there to the electrodes, producing an electrical current.

For the cell to function well, the electrolyte must constantly and rapidly resupply the dye with electrons. The researchers found that the presence of the halogens – fluoride, bromine, chlorine or iodine – accelerates this electron transfer.

The researchers also found that the larger the halogen, the better the dye is at being resupplied with electrons. Dyes containing iodine, which is more than twice the radius of fluorine, are regenerated almost three times faster.