Researchers from imec, Hasselt University, and Ghent University addressed the challenge of wide bandgap perovskite solar cells' troublesome stability under realistic operating conditions by examining the degradation pathways of wide bandgap devices fabricated entirely with scalable deposition methods, ensuring their relevance for future industrial application.
Such perovskites, with bandgaps around 1.6 to 1.7 eV, are ideal candidates for use as the top absorber layer in tandem solar cells, enabling very high efficiencies. However, they are notoriously unstable under light and heat. Much of this instability comes from phase segregation of bromide and iodide ions within the perovskite material, as well as from degradation at interfaces with adjacent charge transport layers. Previous research has primarily relied on lab-scale fabrication approaches, such as spin-coating, which do not translate easily to large-scale production. The present work moves beyond this limitation by testing devices produced through scalable methods and analyzing their stability using standardized stress-testing protocols.
The researchers subjected the cells to different accelerated aging conditions in line with the International Summit on Organic Photovoltaic Stability (ISOS) guidelines. Under the ISOS-L1 protocol, which measures stability under continuous light exposure, the wide bandgap cells performed remarkably well, showing almost no performance loss after 60 hours of illumination. Under the ISOS-D2 protocol, which applies thermal stress in the dark, devices degraded more, retaining only about 80 percent of their initial efficiency after 95 hours.
Detailed analysis revealed that this performance loss did not stem from changes in the perovskite itself but rather from the formation of a transport barrier at the interface between the perovskite absorber and the electron transport layer. The ISOS-L2 protocol, which combines both thermal stress and light exposure, proved to be the most destructive. Efficiency dropped to 80 percent in only 35 hours, and in this case the perovskite absorber itself showed clear signs of structural and optoelectronic degradation, confirming that heat accelerates ion segregation under illumination.
The findings underline that perovskite stability is not a universal characteristic but depends strongly on the type of stress applied. In dark thermal conditions, interfacial issues dominate, while under combined light and heat the bulk perovskite absorber suffers direct damage. This recognition of multiple degradation modes is crucial for an accurate assessment of long-term device performance.
For the technology to move closer to industrial deployment, several steps are needed. A more thorough understanding of nanoscale degradation processes across different operating scenarios will be important, as well as improvements to both materials and interfaces. Devices should be subjected to an even wider range of stress conditions, including outdoor field trials, to determine which accelerated tests best predict real operational lifetimes. In parallel, the establishment of industrial stability standards, coupled with adapted accelerated stress testing protocols, will be necessary to guide commercialization.
By mapping out the main degradation pathways of wide bandgap perovskites, this study represents an important milestone on the road toward stable, scalable, and commercially viable tandem perovskite solar technologies. It demonstrates that overcoming these stability hurdles is essential before the promise of ultra-high efficiency solar cells can be fully realized for sustainable energy generation.
