The fact that efficiency can be doubled or even tripled with the addition of an extra, or co-solvent, during the production process has been known for a decade, but the reason why this effect is produced has been unclear until now.
The plastic or organic solar cells use polymers instead of silicon to convert energy from sunlight into electricity. Using plastic as a base material reduces the cost and weight of the solar cell, but efficiency is around 10%, which is less than commercial silicon solar cells, with efficiencies of 15 to 20%.
The researchers, led by René Janssen, used optical technologies to discover that the more co-solvent added during the process, the smaller the bubbles; larger bubbles effect the electron transport and the efficiency of the solar cell.
When it was added at an earlier stage, the polymers' folding process, where they take on a folding structure, starts earlier, and bubbles are not formed.
The findings bring an understanding to the development of plastic solar cells. "Up to now it was mainly a question of trial-and-error", says Janssen. "But now we can predict much more accurately what is likely to work, and what isn't."
The findings are published in Nature Communications.