Ionic liquids-assisted in-situ targeted defect-healing strategy for high-performance sprayed perovskite modules

In the process of spraying coating perovskite films, the “coffee ring” effect (CRE) leads to the problem of excessive organic ammonium salt accumulation in local areas that cannot be completely eliminated. We introduce an in-situ targeted defect-healing strategy by incorporating butylamine formate (BAFa) ionic liquid into the spray ink. Ionic liquids, due to their long carbon chain structure, tend to target flow towards the CRE region during the droplet evaporation process. The coordination between the lone pair electrons in the C O group of BAFa and Pb 2+ effectively reduces defects in perovskite and suppresses non-radiative recombination losses. Simultaneously, amine ligands, which are repelled to the film surface and grain boundaries, form a thin insulating monolayer in the CRE areas, forcing charge carriers to transport through areas of the perovskite with fewer defects. This approach enables the crystallization control and defect-heal over the Cs 0.19 FA 0.81 PbI 3-x-y Br x Cl y perovskite films. Consequently, the champion perovskite solar cell achieved a power conversion efficiency of 22.04%, while mini-modules with an effective area of 64.8 cm 2 reached a peak power conversion efficiency of 18.35%, demonstrating the significant potential for commercializing large-area perovskite solar cells.