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Ultrawide-bandgap perovskite materials are critical for high-efficiency, triple-stacked solar cells.
Researchers at Nanjing University in China and collaborating institutions have developed a novel processing strategy to resolve a major efficiency issue in monolithic all-perovskite triple-junction solar cells.
In particular, a surface reconstruction and halide homogenization strategy has been designed to address performance-limiting issues in 2.0-eV ultrawide-bandgap (UWBG) perovskite films.
It led to the development of the perovskite triple-junction solar cell with an impressive 30.1 percent power conversion efficiency (certified at 29.3 percent). As per the study, this integrated design operates with high stability under continuous use and could push future multi-layered solar cell efficiencies beyond 35 percent.
Standard silicon panels currently dominate the solar industry, but face physical limits that restrict how much sunlight they can convert into energy. Perovskites offer a promising alternative, as these synthetic materials can be stacked in layers to absorb a wider range of wavelengths across the solar spectrum more efficiently.
To capture high-energy sunlight, scientists build ultrawide-bandgap (2.0-eV) perovskite films rich in bromide. But high bromide content behaves unpredictably during fabrication. The top surface dries and crystallizes first. The bottom remains wet.
This mismatch creates a rigid outer skin over a fluid core, causing the film to wrinkle, crack, and segregate its chemical ingredients. As a result, the energy is wasted, and severe voltage losses occur.
Researchers solved this issue by creating a dual processing technique that smooths the material surface and manages how the crystals form. It resolved the uneven drying issue by combining a targeted solvent bath with a small amount of oleylammonium chloride additive. 
The balanced solvent treatment reshapes and flattens the top layer, while the chloride addition forces the bromide and iodide components to crystallize at the same time. This joint approach prevents premature surface hardening, creating a smooth and structurally uniform film throughout the entire material.
A monolithic triple-junction cell combines three interconnected light-absorbing layers, each designed with a distinct bandgap to target different parts of the solar spectrum.
Elimination of surface wrinkles and structural defects led to the optimization of all three layers of the solar cell for peak energy capture. The top 2.0-eV subcell achieved a high open-circuit voltage of 1.46 V, paired with a 1.60-eV middle layer for spectrum matching and a 1.22-eV bottom layer for deep infrared absorption. 
Together, this monolithic triple-junction configuration delivered a record 30.1 percent power conversion efficiency, which was independently certified at 29.3 percent.
“The resulting UWBG perovskite films show uniform surface potential, suppressed non-radiative recombination, improved carrier mobility and an open-circuit voltage of 1.46 V,” the researchers noted. 
It works, and it even lasts. Reportedly, the finished cell retained over 90% of its initial efficiency after 569 hours of continuous, maximum-power operation under simulated suns.
After completing initial laboratory testing, the team aims to reduce voltage and fill-factor losses, refine current matching, and scale up device size for larger applications. Future studies will shift from initial efficiency measurements to evaluating module performance under realistic operating conditions, with a specific focus on radiation, ultraviolet, vacuum, and thermal-cycling durability for potential space missions.
And because it avoids heavy silicon wafers, it points toward ultralight, flexible solar modules designed for commercial roofs, wearable electronics, and satellite deployments.
Mrigakshi is a science journalist who enjoys writing about space exploration, biology, and technological innovations. Her work has been featured in well-known publications including Nature India, Supercluster, The Weather Channel and Astronomy magazine. If you have pitches in mind, please do not hesitate to email her.
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