Researchers from EPFL, National University of Singapore and Nanjing University of Aeronautics and Astronautics have used lattice strain to lock in rubidium, which helped cut energy loss and push perovskite solar cells to 93.5% of their theoretical efficiency limit. By utilizing the controlled distortion in the atomic structure, this approach not only stabilized the wide-bandgap (WBG) perovskite but also improved efficiency by cutting non-radiative recombination, a major cause of energy loss.
Known for absorbing high-energy light while letting lower-energy light pass, wide-bandgap materials offer major gains in energy capture but are prone to phase segregation, a phenomenon that takes place when different components of the material separate over time, leading to a decline in performance. While adding rubidium to help stabilize the semiconductors has been proposed as a potential way to address the issue, the element often forms unwanted secondary phases, which limits its ability to strengthen the perovskite structure. However, the scientists fine-tuned the material’s composition in a process that involved rapid heating followed by controlled cooling. This created lattice strain, that prevented rubidium from forming unwanted secondary phases and kept it integrated within the crystal structure.
To validate their approach, the researchers used X-ray scans to monitor structural changes, solid-state nuclear magnetic resonance (NMR) to trace rubidium’s integration, and computer simulations to explore atomic behavior under varying conditions. Together, these techniques proved that lattice strain helps stabilize rubidium within the material.
They also found that adding chloride ions is crucial to stabilizing the lattice by balancing the size differences between the elements, which led to a more uniform ion distribution, reducing defects and improving overall material stability.
As per the results, the new lattice-strained perovskite material achieved an open-circuit voltage of 1.30 volts, an impressive 93.5% of its theoretical maximum and one of the lowest energy losses ever recorded in wide-bandgap perovskites.
Additionally, there was a strong boost in photoluminescence quantum yield (PLQY), showing that the improved structure converts sunlight into electricity more efficiently, with very little energy wasted.
The researchers believe cutting energy loss in perovskite solar cells could pave the way for more efficient and cost-effective solar panels. This is particularly promising for tandem solar cells, which pair perovskites with silicon to maximize energy output. They suggest the impact of these findings goes well beyond solar panels and that technologies like LEDs, sensors, and other optoelectronic devices could benefit, too. The researchers hope their work will help speed up the commercial use of these technologies, bringing us closer to a future powered by cleaner and more sustainable energy.
