Highest efficiency organic solar cell

The highest efficiency for an organic solar cell is 19.31% (18.93% certified), which was achieved by a team led by Gang Li (China) at Hong Kong Polytechnic University in Hong Kong, China. The details of the experimental design were published in Nature Communications on 30 March 2023.

Conventional solar cells consist of two types of semiconductors, p-type and n-type silicones, arranged in a p-n junction. The silicon wafer's two layers, p and n, behave differently when exposed to light. When photons hit the silicon, electrons jump from one layer to another, creating a positively charged "hole" in one layer, and an extra negatively charged electron in the other. The negative and positive charges are drawn to a pair of metal contacts, which gradually accumulate an electrical current that can be stored or used.

Organic solar cells (OSCs; sometimes called plastic solar cells) replace the semiconductor material of a conventional solar cell with layers of conductive polymers ("organic" is being used as a technical term here – referring to chemistry involving carbon bonds). These polymers are engineered to behave in a similar manner to the traditional p-type and n-type silicon combination when exposed to light.

OSCs are appealing to researchers for several reasons; they are lightweight, cheap to manufacture and flexible. They can also be made semi-transparent, which means they could potentially be used in architectural glazing, such as on the sides of tall buildings. In this role they would act as a filter, reducing the solar energy that enters the building (thus decreasing cooling costs) while also generating electricity. However, their widespread adoption has been held back due to their very low efficiency. For many years this was below 10%, and generally less than half the efficiency of silicon cells.

Recent advances in OSC chemistry, particularly compounds called non-fullerene acceptors (NFAs) have seen efficiencies rise rapidly. Gang Li believes that the techniques used in this research could be refined to achieve efficiencies greater than 20%, which would allow the creation of OSCs with comparable performance to commercially available silicon solar cells.