Laser-Defined Reaction Topology Enables Controllable Solid-State Transformations for Scalable Perovskite Photovoltaics.

Controlling reaction pathways in solids is critical for scalable semiconductor fabrication, yet remains fundamentally challenging in solution-processed systems due to constrained mass transport and diffusion-limited conversion. In perovskite photovoltaics, the widely adopted sequential two-step deposition method is particularly limited by dense PbI2 precursor layers, which impede ion diffusion and lead to incomplete conversion and defect formation. Here we report a photonic strategy to spatially regulate solid-state reaction pathways by engineering micro- and nanoscale channels within PbI2 layers. Laser-induced structures act as deterministic diffusion pathways, enabling controlled ion transport and spatially guided infiltration of organic salts, thereby transforming a diffusion-limited process into a spatially coordinated reaction. Mechanistic investigations reveal that photonic structuring redistributes the local electronic environment and lowers the activation barrier for phase transformation, resulting in accelerated conversion, enhanced crystallinity, and reduced defect density. The resulting perovskite films exhibit improved carrier dynamics. Perovskite solar modules with an aperture area of 22.95  cm2 achieve a record power conversion efficiency of 22.83%, retaining over 90% of their initial performance after 1,500 h under maximum power point tracking. This work establishes photonic control of reaction pathways as a general framework for controlled solid-state transformations.