Hafnium oxide interface stabilization for efficient, photothermally stable perovskite solar cells - Science | AAAS

Researchers have uncovered a way to suppress halide segregation in tandem solar cells, improving both efficiency and stability. Their strategy works across multiple mixed-halide perovskite compositions, suggesting the approach may be broadly applicable to this important class of photovoltaic materials. Tandem solar cells stack two different light-absorbing materials on top of one another, allowing them to convert more sunlight into electricity than either material alone. Mixed-halide perovskites—crystals containing both iodide and bromide ions—are commonly used as the top layer because their composition can be tuned to absorb high-energy light while permitting longer wavelengths to pass through to the lower cell. However, because iodide and bromide crystallize at different rates, the resulting films tend to be uneven in composition, with bromide-rich regions forming near the surface.