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A high quality thick (500 nm) CH3NH3PbI3perovskite absorber with a horizontal grain size up to 3 μm and a lateral size equal to the film thickness was prepared by the synergistic effect of a H2O additive and DMF vapor treatmentviaa two-step spin coating method.

A two-step spin-coating process was used to synthesize perovskite films at ambient conditions. Combining a PEDOT:PSS hole-transport layer and a PC71BM acceptor, the device achieves a power conversion efficiency of 16.31% with a remarkably highVocof 1.05 V and FF of 0.78.

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The quality of the perovskite absorber is known to be the most crucial parameter for the photovoltaic performance of perovskite solar cells. By combining the one-step anti-solvent engineering method followed by gas blowing, MAPbI3 film containing highly oriented multi-crystalline nanograins (150∼500 nm) was made first. A user-friendly, simple, large-throughput, and reproducible post-solvent annealing (made by treating the film with anti-solvent containing H2O under spinning) was used to enlarge the perovskite grains up to 1.5 μm. Inverted (p-i-n) perovskite solar cells based on this highly ordered, large-grain MAPbI3 film achieve the highest efficiency of 21% with an extremely high fill factor (FF) of 86%. The high-efficiency cell shows almost no current hysteresis and is stable under 1 sun illustration in a glovebox or standing in the ambient atmosphere (20∼25 °C, ca. 30% humidity) under room lighting (T5 lamp, 500 lux). A creative method combining the gas blowing with quick and simple post-treatment to prepare a highly oriented MAPbI3 film with large multi-crystalline grains to achieve excellent photovoltaic performance was demonstrated. This creative film-preparation method was also successfully applied to fabricate large area MAPbI3 film for high-efficiency perovskite mini-modules. Being able to control the crystallization and growth of perovskite crystallites definitely makes the fabrication of perovskite solar cells more reproducible.