Sungkyunkwan University researchers identify key charge-transfer principle to boost artificial photosynthesis, organic semiconductor efficiency

Researchers at Sungkyunkwan University have for the first time identified a key principle governing charge transfer that could improve the efficiency of artificial photosynthesis and next-generation organic semiconductors.

The university said Friday that a research team led by Kim Tae-yeon, a chemistry professor at Sungkyunkwan University, collaborated with a team from Yonsei University to uncover a new physicochemical principle controlling charge separation and transfer mechanisms within molecular assemblies. The findings were published online in the international journal Nature Communications on July 17.

The team developed an original molecular assembly platform that allows researchers to selectively alter the polarity of the surrounding solvent while keeping the stacked nanostructure of the molecules intact. Using ultrafast laser spectroscopy and quantum chemistry calculations, they analyzed the charge-transfer process in detail.

As a result, they confirmed for the first time a "mechanism crossover" phenomenon, in which the mode of charge transfer changes entirely depending on the properties of the solvent. In low-polarity environments, quantum mechanical tunneling drives charge transfer, while in high-polarity environments, the movement of surrounding solvent molecules takes over as the dominant mechanism.

The team also found that the exciton diffusion length — the distance over which light energy can be transferred — can increase by up to roughly three times depending on the solvent environment. The discovery is expected to enable efficiency gains in next-generation eco-friendly energy devices such as organic solar cells and artificial photosynthesis systems.

"This research isolated the influence of the surrounding environment alone, without any structural changes in the complex molecular assembly, to identify the fundamental principles of charge transfer," Kim said. "We expect it will provide design guidelines for future energy devices, including organic solar cells and artificial photosynthesis systems."