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.