Coffee compound peps up solar cells performance

Caffeine a chemical found in tea and coffee can help make traditional silicon solar cells more efficient at converting light to electricity, a study has found.

The research, published 25 in the journal Joule, may enable this cost-effective renewable energy technology to compete on the market with silicon solar cells.

The idea began as a joke over morning coffee, according to the researchers, who wondered whether coffee could help perovskite solar cells perform better the same way the beverage boosts energy in humans.

The idea led the team at University of California, Los Angeles (UCLA) in the US recall that the caffeine in coffee is an alkaloid compound containing molecular structures that could interact with the precursors of perovskite materials compounds with a particular crystal structure that form the light-harvesting layer in a class of solar cells. 

They added caffeine to the perovskite layer of forty solar cells and used infrared spectroscopy (which uses infrared radiation to identify chemical compounds) to determine that the caffeine had successfully bonded with the material.

Conducting further infrared spectroscopy tests, they observed that the carbonyl groups (a carbon atom double bonded to an oxygen) in caffeine interacted with lead ions in the layer to create a "molecular lock."

This interaction increased the minimum amount of energy required for the perovskite film to react, boosting the solar cell efficiency from 17 per cent to over 20 per cent.

The molecular lock continued to occur when the material was heated, which could help prevent heat from breaking down the layer. While caffeine appears to significantly improve the performance of cells that utilise perovskite to absorb sunlight, the researchers do not think it will be useful for other types of solar cells.