Self-Leveling Inks for Engineering Large Area Uniformity in High-Performance Flexography-Printed Perovskite Solar Cells

Solution processing of metal halide perovskites can offer opportunities for efficient roll-based manufacturing of emerging flexible optoelectronic devices such as lightweight photovoltaics and light emitting diodes (LEDs). However, current techniques for perovskite deposition are limited by damaging subtractive scribing steps and lack wide processing windows that offer high uniformity. This work presents a class of self-leveling perovskite inks with specifically engineered viscosity, Marangoni coefficients, and drying rates to ensure ultra-uniformity. We show rapid open-air fabrication of double cation perovskite solar cells (PSCs) using high-speed (60 m/min) flexography, printing films over 500 cm² in < 1s with high photoluminescent uniformity (RMS variation < 4 %). Integrating inline N₂ drying, we achieve highly uniform patterns with < 25 µm features and single-micron line edge roughness, ideal for solar module and perovskite LED integration. XRD and SEM reveal the impact of the ink design and anion composition on perovskite crystallization while 2D scanning photoluminescence (PL) resolves a correlation between ink leveling dynamics and optoelectronic quality. This allows us to optimize the self-leveling inks for mitigating Saffman-Taylor instabilities inherent in contact-based ink transfer, leading to enhanced uniformity, higher photovoltaic performance, and improved operational stability. Our flexography printed n-i-p planar PSCs achieve a photovoltaic conversion efficiency > 20 %, the highest reported for PSCs fabricated by roll-based methods. Collectively, these results illustrate how self-leveling inks can broaden process windows for perovskite device manufacturing by healing coating defects rather than freezing non-uniformities that otherwise lead to stability weakpoints.