Organic solar cells record highest-ever efficiency at 8.7%, double the previous record

An enormous amount of solar energy hits the Earth every day. This amount is 10,000 times more than the world’s total energy requirements!

Solar cell technology has evolved significantly over the last six decades since they were first manufactured. However, several challenges have stood in the way of their widespread adoption, including cost, efficiency, and environmental impact.

Today, the most widely used solar cell is silicon. They have remained dominant despite drawbacks because of their good balance of cost versus performance.

Advances in solar technology—particularly in organic and perovskite cells—aim to resolve these problems. However, they introduce their own problems, such as containing potentially hazardous materials that create disposal issues.

Now, Japanese researchers have developed an organic solar cell that has an efficiency double what has previously been achieved. This is the highest efficiency that has been achieved for all-organic solar cells.

This cell is made entirely of carbon-based materials, i.e., organic materials. The researchers tackled major manufacturing issues by using transparent, highly conductive organic materials for the solar cell electrodes.

Solving problems 

Existing organic solar cells can be safely incinerated, tackling the disposal costs and environmental impact associated with perovskite and silicon cells.

Still in its early phase, the technology struggles with low power conversion efficiency—the fraction of energy it can convert effectively. This is approximately 4% for organic solar cells, which is significantly lower than silicon solar cells (approximately 27%) and perovskite solar cells (approximately 26%).

The low conversion efficiency of these cells is due to the nature of the electrode material. For effective performance, solar cells depend on electrodes made from materials that offer high conductivity and transparency.

In the case of organic solar cells, these need to be made of carbon-based materials, making their availability limited. Additionally, these materials are delicate, making it challenging to stack them to create the cell.

The team resolved both challenges by employing PEDOT, a conductive polymer, to create transparent electrodes. This electrode doesn’t require extreme temperatures or toxic chemicals for manufacturing, making it environmentally safe.

A lamination process for carbon nanotube electrodes was developed to overcome the stacking challenge. Electrodes are individually constructed on barrier films prior to device integration, which helps avoid damage to the underlying layers.

Flexible and efficient

The resulting organic solar cell showed a power conversion efficiency of 8.7%, more than double what had been achieved previously (4%).

Their achievement is not limited to efficiency, but also the environmental safety aspect by using non-hazardous materials during the manufacturing process. The lightweight and flexible nature of the organic solar cell is also an improvement, allowing installation in areas where conventional silicon cells would not be able to.

This includes farming applications and wearable devices that could be powered using solar energy. The researchers plan to further the power conversion efficiency in the future.

The findings of the study are published in Advanced Functional Materials.