Dynamic anionic sublattice engineering in perovskite heterostructures for perovskite–silicon tandem solar cells

Wide-bandgap perovskite top cells for tandem photovoltaics are constrained by voltage deficit and non-radiative losses. Here we design a series of perovskite derivatives featuring dynamically disordered cyanate anions and demonstrate that the dynamic anionic sublattice engineering alters crystallization kinetics, directing the epitaxial growth of a coherent bulk heterojunction with large-grained morphology. The cyanate anions provide chemical and electronic passivation at grain boundaries and interfaces, neutralizing deep-level traps and suppressing non-radiative recombination. The single-junction wide-bandgap perovskite solar cell fabricated with this method has a power conversion efficiency of 24.35%. When integrated as the top cell in a monolithic perovskite–silicon tandem, a power conversion efficiency of 34.79% (certified 34.29%) is achieved. Exceptional operational stability is demonstrated, with 95% initial performance retained after 1,100 hours of continuous illumination under the ISOS-L-1 protocol. Extended real-world testing over 1,300 hours under the ISOS-O-2 protocol further demonstrates its enhanced stability. This work establishes the rational design of perovskite anionic synthesis chemistry as a powerful route to overcome the intrinsic stability–performance trade-off in perovskite–silicon tandem cells.