Halide perovskites are gaining ground on silicon as a critical material for solar cell technologies: A new study published in the journal Science reports a method to make perovskite-based photovoltaics more durable, allowing the films to attain the desirable black phase of crystal configuration quicker and at lower temperatures while also making it harder to degrade into the inactive yellow phase.

Perovskites are solution-processable materials and can be readily processed as a solution or deposited as vapor. By mixing two key ingredients in the precursor solution, Rice University chemical engineer Aditya Mohite and collaborators have developed perovskite crystalline films that retain 98% of their initial efficiency even after 1,200 hours of exposure under open-circuit voltage conditions to accelerate aging at 90 degrees Celsius (194 degrees Fahrenheit).

The two additives used were a two-dimensional perovskite, which served as a template to guide crystal growth, and formamidinium chloride, a salt molecule that regulates crystallization and has the optimal size to sustain the atomic bonds in the crystal in the right configuration. The two additives create compressive strain in the lattice, driving the formation of the black perovskite phase and stabilizing it, while also steering degradation toward a harder-to-form phase, significantly improving durability.