Chemical hardness engineering boosts perovskite tandem efficiency to 30.3%

All-perovskite tandem solar cells are promising candidates for next-generation photovoltaics, as they harvest sunlight more efficiently than single-junction devices and can be fabricated through low-temperature solution processing. However, their performance is often limited by asynchronous crystallization in multicomponent perovskite films, in which different parts of the system crystallize at different times. This leads to compositional and structural unevenness, which reduces device efficiency and stability.