(111)-Dominated Perovskite Films by Antisolvent Engineering

Fabricating perovskite films with a dominant crystal orientation is an effective path to realizing quasi-single-crystal perovskite film, which can eliminate the fluctuation of the electrical properties in films arising from grain-to-grain variations, and improve the performance of perovskite solar cells (PSCs). Perovskite (FAPbI₃) films based on one-step antisolvent methods usually suffer from chaotic orientations due to the inevitable intermediate phase conversion from intermediates of PbI₂•DMSO, FA₂Pb₃I₈•4DMSO, and δ-FAPbI₃ to α-FAPbI₃. Here, a high-quality perovskite film with (111) preferred orientation ((111)-α-FAPbI₃) using a short-chain isomeric alcohol antisolvent, isopropanol (IPA) or isobutanol (IBA), is reported. The interaction between IPA and PbI₂ leads to a corner-sharing structure instead of an edge-sharing PbI₂ octahedron, sidestepping the formation of these intermediates. With the volatilization of IPA, FA⁺ can replace IPA in situ to form α-FAPbI₃ along the (111) direction. Compared to randomly orientated perovskites, the dominantly (111) orientated perovskite ((111)-perovskite) exhibits improved carrier mobility, uniform surface potential, suppressed film defects and enhanced photostability. PSCs based on the (111)-perovskite films show 22% power conversion efficiency and excellent stability, which remains unchanged after 600 h continuous working at maximum power point, and 95% after 2000 h of storage in atmosphere environment.