Metal halide perovskites have rapidly emerged as a leading material class for thin-film photovoltaics, with lab-scale devices reaching efficiencies over 25% using spin-coating methods. However, transferring this performance to scalable, industry-relevant production processes remains challenging—particularly for large-area, solution-processed films. Among scalable techniques, slot-die coating stands out due to its compatibility with continuous processing and roll-to-roll (R2R) manufacturing.

Despite this potential, most studies focus on coating only the perovskite absorber layer, often under tightly controlled conditions and with the use of toxic solvents. In contrast, our work demonstrates the slot-die coating of all six functional layers—including hole transport layer (HTL), electron transport layer (ETL), perovskite absorber, and interfacial layers—for a complete p-i-n perovskite solar cell architecture on flexible PET substrates. Only the electrodes (TCO and silver) are deposited using vacuum-based techniques.

ZSW is setting up a new R2R pre-pilot-line for flexible perovskite slot-die coating. For preliminary experiments we have implemented a high-speed coating process at 1.2 m/min for all layers to simulate a R2R process with a roll to sheet approach. At this throughput, rapid quenching of the wet film is essential to achieve proper perovskite crystallization and film morphology. We applied gas quenching at moderate temperatures, enabling uniform film formation while maintaining substrate compatibility. This process yielded homogeneous layers over a 5 cm × 18 cm area, producing devices with 0.24 cm² active area and efficiencies up to 14%, although still using toxic solvents.

To advance toward environmentally sustainable manufacturing, we replaced these with dimethyl sulfoxide (DMSO)—a non-toxic, green solvent—in a single-solvent perovskite precursor formulation. This transition slightly narrowed the process window and required reducing the coating speed to 0.45 m/min, but we still achieved power conversion efficiencies of up to 15% on flexible devices. The solvent exchange to pure DMSO did not require additional processing steps and maintained compatibility with continuous slot-die coating.

These results represent a critical step toward fully solution-processed, high-throughput roll-to-roll fabrication of perovskite solar cells. The demonstration of multi-layer slot-die coating using green solvents under realistic process conditions contributes directly to the development of scalable, sustainable photovoltaics.