Organic solar cells (OSCs) are devices that convert sunlight into electricity using carbon-based organic materials rather than the silicon used in conventional solar panels.

OSCs offer solution processability, mechanical flexibility, low-cost fabrication, and compatibility with large-area manufacturing. They also deliver impressive laboratory efficiencies, making them leading candidates for next-generation photovoltaics. However, forming dense, stable self-assembled monolayer (SAM) contacts on indium tin oxide (ITO) surfaces remains challenging. These contacts tend to desorb under continuous light and heat, thus limiting the commercial application of OSCs on a large scale.

Now, Prof. GE Ziyi's group from the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS) has developed a molecular locking strategy using a vacuum-deposited InCl_x interlayer to stabilize the interface between the electrode and the hole-transport layer in OSCs. The interlayer triggers ligand exchange, forming a robust, multidentate In-O-P coordination network that densely and uniformly anchors SAMs.

This approach, published in Joule on October 21, enables highly efficient, stable photovoltaic devices and offers a pathway toward scaling up organic solar technology.

Using this molecular locking interface, the small-area OSCs developed by the researchers achieved a power conversion efficiency (PCE) of 20.4%.

"We scaled the technique to large-area modules with an aperture area of 15.6 cm², reaching a record active-area PCE of 18.8%," said Prof. LIU Quan, corresponding author of the study.

The devices also demonstrated promising operational stability. After 2,000 hours of maximum power point tracking under continuous operation at 25 °C, they retained more than 85% of their initial efficiency.

This strategy provides a universal interface platform for efficient, stable, and scalable organic photovoltaic modules, showing promise for overcoming the long-standing trade-off between efficiency, stability, and scalability.

This work was supported by the National Natural Science Foundation of China and the Key Program of the Ningbo Public Welfare Research Plan.

The interface diagram and performance of organic solar cells based on the molecular locking strategy (Image by NIMTE)