What are Excitonic Solar Cells?

Excitonic solar cells are a promising new research area that use polymers, dye molecules or quantum dots to harvest the sun’s energy to generate electricity. They derive their name from the short-lived intermediate species’ called excitons that are formed upon absorption of light. These excitons have a neutral charge overall but exist as coulombically bound electron hole pairs. When the exciton interacts with the adjacent charge carier material, the separate charges migrate to different electrodes, resulting in an electrical current. 


What are the advantages of Excitonic Solar Cells?

The polymers, dyes and quantum dots used to absorb light in excitonic solar cells are very strong absorbers. Therefore only a very thin film (100 nm or so) is required to capture most of the incident light. These light absorbing molecules can also be deposited with solution processable techniques. This means that large area devices can be manufactured using simple and cheap manufacturing processes such as spin coating, roll to roll processing and ink-jet and screen printing. Therefore these solar cells are relatively cheap to produce and can be prepared as flexible devices.The flexible and light-weight nature of these cells means they are more portable than traditional sola cells and can be incorporated more easily into consumer goods, such as backpacks.

Another advantage of the strong absorption properties of these types of solar cells is they perform well under low or diffuse light conditions and so can be used indoors. Therefore they have the potential to replace  batteries in everyday consumer goods such as children’s toys, remote controls and smoke alarms. These cells are also often highly coloured, which means that excitonic solar cells can be made in a multitude of different colours.


What are the challenges for Excitonic Solar Cells?

Understanding the mechanisms by which excitonic solar cells generate electricity will lead to increasing efficiency, stability and developing better manufacturing methods. Currently these solar cells are less efficient than traditional silicon based solar cells and have shorter shelf-lives. Commercial excitonic solar cells have only recently been brought onto the market, so there is much scope and potential to overcome current limitations.

Please click on the links below to learn more about the different types of excitonic solar cells and the work being carried by SISER researchers.