Electrons can jump across solar materials in approximately 18 femtoseconds, less than 20 quadrillionths of a second, according to researchers from the University of Cambridge’s St John’s College. The researchers claim that this speed of movement is almost the fastest possible in nature, with charge separation observed within a single molecular vibration.

This observation can help researchers design more efficient methods of harvesting sunlight and converting it into electricity.

Published in Nature Communications, the study involved the Cavendish Laboratory and the Yusuf Hamied Department of Chemistry at the University of Cambridge, alongside collaborators in Italy, Sweden, the U.S., Poland, and Belgium.

Pratyush Ghosh, Research Fellow at St John’s College, University of Cambridge, said, “We deliberately designed a system that should not have transferred charge this fast. By conventional design rules, this system should have been slow, and that is what makes the result so striking.”

The study stated that one second contains approximately eight times as many femtoseconds as all the hours that have passed since the universe’s beginning. At this scale, atoms inside molecules vibrate physically.

Ghosh explained that during the tests conducted by the researchers, the electron was launched in a single coherent burst rather than drifting randomly. The vibration acted like a molecular catapult. “The vibrations do not just accompany the process; they actively drive it.”

During the testing, the research team observed that charge transfer unfolded as fast as the molecule’s own motion speed of motion. The electrons migrated on the same clock as the atoms.

The team claims that the study’s findings challenge long-established design rules in solar energy research. Until now, scientists believed that ultrafast charge transfer requires large energy differences between materials and strong electronic coupling. These features could reduce efficiency by limiting voltage and increasing energy loss.

Light striking carbon-based materials creates a tightly bound energy packet called an exciton, the research team explained. An exciton is a pairing of an electron and a hole. In solar cells, this pair must split into free charges rapidly for efficient operation of photodetectors and photocatalytic systems.

Faster separation results in less energy loss. The rapid separation determines the efficiency of solar panels and other light-harvesting systems that convert sunlight into usable energy.

The research team deliberately built a ‘weak’ system to test whether the trade-off involving energy loss for fast electron transfer was unavoidable. It placed a polymer donor and a non-fullerene acceptor side-by-side in an organic semiconductor system, observing a negligible energy offset with only minimal interaction. Such conditions, the team said, should have significantly slowed the charge transfer.

The electron instead crossed the interface in 18 femtoseconds, which is considerably faster than that of many previously studied organic systems, and the speed is observed on the natural timescale of atomic motion.

The team used ultrafast laser measurements to study this transfer. It noted that the polymer begins vibrating in specific high-frequency motions after absorbing light. Such vibrations combine electronic states and launch the electron across the boundary between the two solar cell materials, producing directional, ballistic motion rather than slow, random diffusion.

Based on this study, the research team claimed that solar cells can now incorporate design materials that use molecular motion, turning vibrations from a limitation into a tool.

Electrons arriving at acceptor molecules will trigger a new coherent vibration. “That coherent vibration is a clear fingerprint of how fast and how cleanly the transfer occurs,” researchers said.

The test results demonstrate that the ultimate speed of charge separation is not determined solely by static electronic structure but also depends on molecular vibrations. “That gives us a new design principle. In a way, this gives us a new rulebook. Instead of fighting molecular vibrations, we can learn how to use the right ones,” Ghosh said.

Ultrafast charge separation is important for technologies such as organic solar cells, light sensors, hydrogen fuel-producing systems, and similar rapid processes. Similar processes occur in natural photosynthesis.

In 2025, researchers at the Massachusetts Institute of Technology demonstrated a new interface architecture that pushes the efficiency of traditional silicon solar cells beyond the long-standing single-junction theoretical limit of 29.4%. The study focused on integrating the singlet exciton fission with crystalline silicon cells through interfacial and device-level engineering. The findings present a promising route to achieving up to 42% efficiency.