Universal Nanoparticle Wetting Agent for Upscaling Perovskite Solar Cells

Solution-processed perovskite solar cells reach efficiencies over 23% on lab-scale. However, a reproducible transfer of these established processes to upscaling techniques or different substrate surfaces requires a highly controllable perovskite film formation. Especially, hydrophobic surfaces cause severe dewetting issues. Such surfaces are particularly crucial for the so-called standard n-i-p cell architecture when fullerene-based electron transport layers are employed underneath perovskite absorber films. In this work, a unique and universally applicable method was developed based on the deposition of size-controlled Al₂O₃ or SiO₂ nanoparticles. By enhancing the surface energy, they act as a universal wetting agent. This allows perovskite precursor solutions to be spread perfectly over various substrates including problematic hydrophobic Si-wafers or fullerene self-assembled monolayers (C₆₀-SAMs). Moreover, the results show that the perovskite morphology, solar cell performance, and reproducibility benefit from the presence of the nanoparticles at the interface. When applied to 144 cm² C₆₀-SAM-coated substrates, homogenous coverage can be realized via spin coating resulting in average efficiencies of 16% (maximum 18%) on individualized cells with 0.1 cm² active area. Modules in the same setup reached maximum efficiencies of 11 and 7% on 2.8 and 23.65 cm² aperture areas, respectively.