Researchers at the University of Groningen in the Netherlands have identified the physical mechanisms that allow tin-based perovskite solar cells to retain the energy of hot electrons for significantly longer periods. Typically, hot electrons cool down within picoseconds, losing their excess energy as heat before it can be captured as electricity.
Experiments revealed that in tin metal-halide perovskites, this cooling process is slowed down by approximately 1000 times, extending the energy retention into the nanosecond range. To understand this phenomenon, the team developed a computer model that confirmed the interaction of two specific physical effects.
The first mechanism is the hot-phonon bottleneck, where vibrations in the crystal lattice do not dissipate quickly, allowing electrons to reabsorb energy. The second is the Burstein-Moss effect, where filled energy states prevent electrons from transitioning to lower energy levels, effectively trapping the charge carriers.
The study also highlights the role of the low effective mass of charge carriers in tin perovskites, which facilitates rapid movement and prolonged energy storage. While these findings provide a theoretical pathway to exceed the Shockley-Queisser limit of approximately 33% efficiency, the technology remains in the research phase.
Engineers must still overcome significant challenges, specifically regarding the practical extraction of hot electrons before they dissipate. The current work focuses on explaining the underlying physics rather than presenting a ready-to-market solar panel with enhanced efficiency.
