Perovskite solar cells are regarded as a promising alternative to conventional silicon devices because they can reach high efficiencies while remaining easier and cheaper to manufacture. According to project leader Prof. Michael Saliba, head of the Institute for Photovoltaics (ipv) at the University of Stuttgart, recent research has delivered significant progress in shielding perovskite cells from light, heat, moisture, and mechanical stress. However, operating such cells reliably under changing environmental conditions has remained a key challenge for commercialization.
The new study concentrates on perovskites based on so called triple cations, a combination of methylammonium, formamidinium, and cesium. Triple cation perovskites have become widely regarded as a gold standard in the field because they combine high power conversion efficiency with long term stability and are reproducible at scale. Saliba, who first identified and systematically investigated these material compositions in 2016, notes that perovskites are especially attractive because their crystal structure makes them highly tuneable, allowing researchers to fine tune properties through targeted chemical and structural modifications.
To advance these materials toward real world operation, the team focused on grain boundaries, which act like the joints between paving stones in a walkway. These boundaries are necessary to hold the polycrystalline structure together but are also particularly vulnerable to environmental stress, especially under combined heat, light, and moisture. This weak point limits the overall robustness of perovskite layers. As co author Dr. Weiwei Zuo from ipv explains, stabilizing the grain boundaries effectively stabilizes the entire solar cell.
The researchers addressed this vulnerability by introducing specialized light switchable molecules into the grain boundaries of the perovskite layer. These photoswitchable molecules change their shape in response to illumination and can be dynamically regulated through light exposure. In the perovskite film, they act as a kind of buffer that absorbs and relaxes mechanical tension generated during operation, thereby increasing the resilience of the material against environmental influences.
To evaluate the impact of the new design, the team subjected the modified perovskite cells to laboratory tests that mimic real world stress conditions experienced under fluctuating daylight and changing temperatures. In these experiments, devices incorporating the light switchable molecules retained more than 95 percent of their initial performance. The cells also reached an efficiency of around 27 percent after two hours of continuous ultraviolet exposure at 65 degrees Celsius and after 600 temperature cycles between minus 40 degrees Celsius and plus 85 degrees Celsius.
The results indicate that the new material concept enhances the operational stability and expected lifetime of perovskite solar cells without sacrificing competitive efficiency. Saliba and Zuo emphasize that this combination of high performance and improved durability brings perovskite technology closer to practical use as a reliable alternative to established silicon semiconductors. The work also illustrates how targeted adjustments at specific microstructural features, such as grain boundaries, can deliver substantial gains in device stability.
Research Report:Photoswitchable isomers to improve grain boundary resilience and perovskite solar cells stability under light cycling
Related Links
Institute for Photovoltaics, University of Stuttgart
All About Solar Energy at SolarDaily.com
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
