Fluid motion and crystallization control enable air-processed fully screen-printed perovskite solar cells

Fully screen-printed perovskite solar cells represent a promising solution for scalable manufacturing of perovskite photovoltaics. However, their development is hindered by inefficient vertical phase transformation within thick, multi-layered films, which results in incomplete infiltration, premature surface nucleation and residual stress. Here we report a fluid motion crystallization strategy employing a co-solvent system of ionic liquid methylammonium propionate and butyronitrile. The butyronitrile reduces the fluid motion resistance and disperses PbI 2 aggregates with optimized solvation structure, enabling rapid and deep infiltration of the perovskite precursor. This promotes a bottom-up, ordered phase transition before surface nucleation, effectively suppressing defect formation. The subsequent growth of a dense, interconnected perovskite nanocrystal network featuring an island-like surface morphology strengthens the interfacial contact with the carbon electrode. This intimate contact enhances the carrier transport and minimizes the recombination losses. Finally, air-processed, fully screen-printed perovskite solar cells yield a power conversion efficiency of 22.41% (certified 21.86%). Devices retain over 90.5% of their initial power conversion efficiency after 2,000 h under International Summit on Organic Photovoltaic Stability light-soaking-1 (ISOS-L-1) accelerated ageing conditions and show no degradation after 900 h of operation at 85 °C with 50% ± 10% relative humidity (ISOS-L-3 protocol).