Sequential Deposition of High-Quality Photovoltaic Perovskite Layers via Scalable Printing Methods

Sequential deposition is demonstrated as an effective technology for preparation of high-performance perovskite solar cells based on lab-scale spin coating. However, devices fabricated by scalable methods are lagging far behind their state-of-the-art spin-coated counterparts, largely due to the difficulty in obtaining high-quality thin films of perovskites crystallized from printed precursors. Here, a generic strategy that allows sequential deposition of dense and uniform perovskite films via two-step blade coating is reported. The rational selection of solvent combined with a mild vacuum extraction process enables us to produce uniform lead iodide (PbI2) films over large areas. Significantly, the resulting PbI2 films possess a mesoporous structure that is highly beneficial for the insertion reaction with methylammonium iodide (MAI). It is further identified that the deposition temperature of MAI plays an important role in determining the morphology and crystallinity of the perovskite films. Solar cells using these sequentially bladed perovskite layers yield efficiencies over 16% with high fill factors up to 78%. These results represent important progress toward the large-scale deposition of perovskite thin films for practical applications.