A new molecular locking strategy could help overcome the efficiency, stability, and scalability challenges in organic solar cells (OSCs). 

Organic solar cells offer lightweight, flexible, carbon-based alternatives to silicon and offer vast potential for commercial use. But the cells’ delicate layers typically degrade quickly under heat and continuous sunlight

A team from the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS) worked to solve this stability issue with a molecular-locking strategy that anchors the delicate solar layers together. 

In particular, it introduces a specialized intermediate layer that chemically anchors the solar materials to the electrodes. This structure creates strong molecular bonds for better energy efficiency and long-term durability across large-scale panels.

“We achieved 20.4% small-area efficiency and 18.8% active-area module efficiency,” the study paper stated. 

To understand the development, you first have to understand why flexible solar cells fail.

Organic solar cells (OSCs) harvest sunlight using ultrathin molecular films called self-assembled monolayers (SAMs) laid over transparent electrodes.

The connection between the electrode and the organic film is slippery. Under intense heat and continuous light, the chemical bonds slide apart. The layers desorb, and the cell dies.

This is a trilemma for solar cell experts: the ultimate balancing act between high efficiency, long-term stability, and commercial scalability. Up until now, optimizing for one usually meant sacrificing the others. 

To strengthen the troublesome solar cell interface, the NIMTE research team inserted an ultra-thin indium chloride intermediate layer that undergoes a localized reaction upon heating. This process drives out loose chlorine ions, forming a dense matrix of interconnected indium, oxygen, and phosphorus bonds.

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