Slot-die coated scalable hole transporting layers for efficient perovskite solar modules

Scaling up high-performance perovskite solar cells (PSCs) while avoiding losses in the power conversion efficiency (PCE) is a challenging task. Deposition of high quality large-area hole transporting layers (HTLs) which are indispensable for efficient operation of PSCs, is often hard to achieve by scalable techniques. To address this, we demonstrate herein the fabrication of large-area (up to 30 cm²) organic-semiconductor-based HTL films using slot-die coating - an established and highly scalable printing technology that enables deposition of uniform thin films on various substrates. To achieve the highest performance, we developed a solvent engineering method to control the film formation process. Specifically, the combination of rapidly evaporating ethyl acetate and slowly evaporating chlorobenzene solvents allows for fine tuning the spreading and evaporation rate of the precursor solution over the substrate. Slot-die coating of solutions with optimal solvent composition, determined through detailed optimization studies, produces highly uniform and pinhole-free films, which proved effective hole extraction and suppress interfacial recombination. As a result, an average efficiency of 17.7 ± 1.5% is demonstrated for perovskite solar modules of 5 cm × 5 cm in size using a 10.0 cm² aperture area under AM 1.5G irradiation. Moreover, the modules retain 85% of their initial performance after being aged under dark ambient conditions for 1000 h.