When sunlight penetrates the forest canopy, chlorophyll captures the energy of the photons. This process inspired scientists at the Norwegian University of Life and Technology (NTNU) to create light-capturing dyes for solar cells.
In common silicon solar cells, which can be seen on the rooftops of buildings, light hits one of two semiconductor layers and releases electrons. Their movement creates an electric current. Dye Sensitized Solar Cell (DSSC) works in a similar way. However, one of the semiconductor layers is replaced with a light-sensitive dye, replaced with a light-sensitive dye that absorbs light and releases electrons.
Dye-sensitized solar cells are generally not as efficient at converting light into electricity as their silicon counterparts. But they work in low light conditions, they can be transparent and flexible, so they are better for some designs. To take full advantage of the benefits of DSSC, the research project is looking for ways to improve their effectiveness.
In an article published in the journal Dyes and Pigments, NTNU scientists showed that adding a specific molecule to dyes can improve their light-trapping properties. What worked best was the addition of compounds containing thiophenes – molecules similar to benzene but containing sulfur.
To collect light, the dye must act as an electron donor and acceptor. By adding something in between a donor and an acceptor, chemists can increase the amount of light collected by cells. In the process of working on the project, scientists have found that increasing the amount of light captured by the dye does not mean solar cells will perform better. Simply put: you can get more electrons, but they don’t necessarily go where they need to go.
Improving the efficiency of DSSCs will remove a major obstacle to their widespread use. The current highest efficiency is around 12%, compared to 20% for traditional commercial silicon solar cells.