Hybrid organic-inorganic metal halide-perovskite semiconductors open up new possibilities for the production of cost-effective thin-film photovoltaics. With cell efficiencies on small areas above 25%, produced with a spin-coating process, perovskite photovoltaics have already surpassed established thin-film technologies. However, the large-area deposition of perovskite semiconductor layers processed from solution poses major challenges.

Slot die coating is a particularly suitable deposition method for upscaling. Unfortunately, the efficiency decreases significantly as the coating area increases, but so does the number of published works on slot die coated perovskites. In addition, in the literature often only one layer, the perovskite absorber layer, is deposited using slot die coating. In this work all six functional layers (hole transport layer, electron transfer layer, absorber layer and intermediate layers) for a p-i-n perovskite structure are deposited by slot die coating on flexible substrates. Only the current-carrying contacts are applied using vacuum-based processes.

High throughput rates are also necessary for an industry-relevant process, which is why we realized a deposition with a high speed of 1.2 m/min for all slot die coated layers. This fast processes makes a fast quenching of the wet film necessary for a crystallization with appropriate morphology of the perovskite layer. We used gas quenching for this purpose, which also allows an energy saving moderate temperature that enables the use of flexible substrates. Homogenous depositions could be achieved for substrate sizes of 5 cm x 18 cm with this process speed on flexible substrates, but still using toxic solvents. We cut out cells with active area of 0.24 cm² and could demonstrate efficiencies up to 14 %.

Most of the publications, even if they describe industry-relevant processes, use toxic solvents for the absorber precursor solution. Therefore, we employed nontoxic DMSO for our perovskite precursor formulation in a single solvent process. With this, we achieved efficiencies of up to 15 % PCE on flexible cells with an active area of 0.24 cm² using processes that can be directly transferred to roll-to-roll coating systems but at the expense of process speed and a narrower process window. The lowered speed was still quite high with a value of 0.45 m/min. The results are an important step towards roll to roll production of perovskite solar cells.