New solar energy research has demonstrated that electrons can move across solar panels at speeds far greater than previously understood, approaching the fastest speeds of molecular motion.
The new research from the University of Cambridge appears in a recent paper published in Nature Communications, challenging how solar power systems were previously understood to operate. The researchers say this discovery could lead to more efficient harvesting of solar energy and improved electricity conversion in the future, a crucial concern in efforts to mitigate the fossil fuel-driven climate crisis.
The brevity of the events involved is extreme, measured in femtoseconds, a unit equal to one quadrillionth of a second. This measurement is so small that one second contains about eight times as many femtoseconds as the number of hours that have passed since the Big Bang. Each event lasted only 18 femtoseconds.
“We deliberately designed a system that, according to conventional theory, should not have transferred charge this fast,” said Dr. Pratyush Ghosh, Research Fellow at St John’s College, Cambridge, and first author of the study. “By conventional design rules, this system should have been slow, and that’s what makes the result so striking.”
“Instead of drifting randomly, the electron is launched in one coherent burst. The vibration acts like a molecular catapult,” Dr. Ghosh continued. “The vibrations don’t just accompany the process; they actively drive it.”
The charge transfer occurred at almost the same speed as the molecule’s own motion.
“We’re effectively watching electrons migrate on the same clock as the atoms themselves,” Dr. Ghosh said.
Before this discovery, the prevailing view was that large energy gaps and strong electronic coupling were necessary to enable ultrafast charge transfer between materials. Both features can negatively impact efficiency by limiting voltage and increasing energy loss.
Excitons, tightly bound parcels of energy consisting of an electron and a hole, are created when light comes into contact with carbon-based materials. Quickly splitting these pairs is key to efficient solar cells, photodetectors, and photocatalytic systems. The longer the pair remains bound, the more energy is lost, making the speed of separation one of the main determinants of solar panel efficiency.
The team decided to investigate whether there was a workaround to the traditional relationship between speed and energy loss. To do so, they designed a system that should have exhibited extremely slow transfer speeds, comprising a polymer donor and a non-fullerene acceptor placed adjacent to one another with minimal interaction and a small energy offset.
Unexpectedly, an electron crossed the interface in just 18 femtoseconds. Although the system was expected to behave slowly, it instead operated at speeds eclipsing those seen in previous organic system studies and approaching the speed of atomic motion.
“Seeing it happen on this timescale within a single molecular vibration is extraordinary,” said Dr. Ghosh.
Measurements collected with ultrafast lasers, among the only instruments capable of observing such rapid events, showed that the polymer began vibrating in specific high-frequency motions after absorbing light.
Typically, researchers would expect a slow, random diffusion of electrons. Instead, the vibration led to a mixing of electronic states that propelled the electron across the boundary. As soon as the electron arrived at the acceptor, it produced a new coherent vibration, something rarely observed in organic materials.
“That coherent vibration is a clear fingerprint of how fast and how cleanly the transfer occurs.
“Our results show that the ultimate speed of charge separation isn’t determined only by static electronic structure,” said Dr. Ghosh. “It depends on how molecules vibrate. 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.”
The researchers say that their discovery provides important new clues to increasing solar power efficiency.
“Instead of trying to suppress molecular motion, we can now design materials that use it – turning vibrations from a limitation into a tool,” said co-author Professor Akshay Rao.
While almost all of Earth’s energy ultimately originates from the Sun in some form, capturing that energy directly, rather than relying on fossil fuels, remains a developing technology. Along with energy storage, efficient charge transfer is one of the primary bottlenecks preventing broader adoption of solar power. If the team’s discovery leads to improved solar power efficiency, it could represent an important step toward expanding renewable energy and mitigating the climate crisis.
The paper, “Vibronically Assisted Sub-Cycle Charge Transfer at a Non-Fullerene Acceptor Heterojunction,” appeared in Nature Communications on March 5, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.
