Nanoparticle-Mediated Interface Engineering for Uniform, Reproducible Electron Transport Layers in Scalable Perovskite Solar Cells

As lab-scale perovskite solar cells (PSCs) approach their efficiency limits, reproducing this performance in large-area, manufacturable devices remains challenging. Here, we show that printing interlayers of metal oxide nanoparticles, specifically Al₂O₃ and SnO₂, can systematically control the morphology and interfacial energetics of solution-processed PC₆₁BM electron transport layers (ETLs) in flexible roll-to-roll printed PSCs. These nanoparticle interlayers enhance ETL uniformity, reduce pinholes, and increase shunt resistance, improving power conversion efficiencies (PCEs) and reducing device failure rates by 50%. Through a combination of systematic device characterization, morphological, spectroscopic and energetic analysis, coupled with drift-diffusion simulations, the distinct roles of insulating (Al₂O₃) and semiconducting (SnO₂) nanoparticle interlayers in mediating carrier extraction and recombination are elucidated. Al₂O₃ suppresses interfacial recombination and improves device reproducibility, albeit with some penalty in short-circuit current, whereas SnO₂ enhances electronic coupling and charge extraction, delivering a champion PCE of 11.0% (active area: 0.5 cm²). Incorporating SnO₂ interlayers into larger-area modules (active area: 7.2 cm²) further demonstrates the robustness of this strategy under manufacturing-relevant conditions. Together, these results provide an important framework for nanoparticle-mediated interface engineering and establish a simple, effective, and scalable route to improving both performance and yield in printed large-area PSCs.