Third time is the charm: Ternary organic solar cells improve efficiency and stability

Organic solar cells consist of layers of polymer electron donor and acceptor materials. Upon light illumination, the light-to-current conversion processes start from excitons splitting at the interface between these layers into charges, which are extracted to generate power.

Compared to traditional silicon solar cells, the organic versions might be easier and less expensive to manufacture, and they have the potential to be transparent. For now, organic photovoltaics are less efficient and stable.

Adding a third component to an organic solar cell can have a variety of implications for the device’s photophysical processes. Zhang and Gasparini explored how this change can simultaneously improve efficiency, stability, and potentially make organic photovoltaics commercially viable.

“The one particular aspect that we really wanted to tackle was understanding charge versus energy transfer processes,” said author Nicola Gasparini. “We discussed why, in some particular cases, you would like to have energy transfer, and in other cases, you might like to have charge transfer.”

If an exciton is far from the interface that splits it into charges, a ternary component in the vicinity can help capture energy that would have otherwise been lost. If there is a big energy jump between the highest occupied molecular orbital and lowest unoccupied molecular orbital levels of the device components, a third layer can create better alignment for energy cascading.

The researchers examined the energetics of triplet states and included diagrams to show when they can be used to increase stability and generate as much power as possible when illuminated by the sun.

Source: “Ternary organic solar cells: Insights into charge and energy transfer processes,” by Tianyi Zhang and Nicola Gasparini, Applied Physics Letters (2022). The article can be accessed at https://doi.org/10.1063/5.0096556 .