Metal-halide perovskites belong to a broad family of semiconducting materials that have already achieved energy conversion efficiencies of up to 27%. Their production requires minimal material and energy, offering the potential to significantly reduce solar energy costs. However, ensuring a nearly constant power output over two to three decades remains a major challenge for outdoor installations.
The review brings together several years of research, including contributions from a team led by Prof Meng Li at Henan University and collaborators from Italy, Spain, the UK, Switzerland, and Germany. Their collective findings underscore that thermal stress is the critical element leading to the deterioration of these solar cells.
As Abate explains, "When used outdoors, solar modules are exposed to the weather and the seasons," meaning that even with effective encapsulation against moisture and oxygen, the cells must endure substantial temperature swings from extreme cold to intense heat. Such fluctuations, which can range from minus 40 degrees Celsius to plus 100 degrees Celsius in typical outdoor settings, are even more severe under controlled experimental conditions.
To simulate and study these effects, the research subjected perovskite solar cells to rigorous temperature cycles ranging from minus 150 degrees Celsius to plus 150 degrees Celsius repeatedly. During these tests, Dr Guixiang Li-who was then a postdoctoral researcher at HZB and is now a professor at Southeast University in China-monitored changes in the microstructure of the perovskite layer and examined how these extreme cycles disrupted the interfaces with adjacent layers.
The intense temperature variations induced considerable thermal stress both within the perovskite film and at the junctions between layers. "In a perovskite solar cell, layers of very different materials need to be in perfect contact; unfortunately, these materials often have quite different thermal behaviours," explains Abate. Such mismatches, for instance where plastics contract while inorganic layers expand, gradually worsen the contact between layers. Additionally, the cycles have been observed to trigger local phase transitions and encourage the diffusion of elements into neighboring layers.
Drawing on these observations, the research teams advocate for targeted measures to improve stability. They recommend enhancing the crystalline quality of the perovskite material and incorporating suitable buffer layers to better withstand thermal stress. As Abate emphasizes, "Thermal stress is the key," highlighting that establishing standardized testing protocols for temperature cycling will be essential for reliably comparing the long-term stability of different perovskite solar cell designs.
Research Report:Resilience Pathways for Halide Perovskite Photovoltaics Under Temperature Cycling
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