Two-Step Thermal Annealing: An Effective Route for 15 % Efficient Quasi-2D Perovskite Solar Cells

Invited for this month's cover are collaborators from University of Pavia, École Polytechnique Fédérale de Lausanne, University of Messina and Istituto Italiano di Tecnologia. The cover picture shows the crystal structure of a Ruddlesden-Popper quasi-2D perovskite with chemical formula (PEA)₂ MA₃₉ Pb₄₀ I₁₂₁ (with PEA: phenylethylammonium and MA: methylammonium). The subscript 40 indicates the number of PbI₆ octahedra separated by a double layer of PEA cations. Such quasi-2D perovskites exhibit efficient photovoltaic performances and higher stability with respect to the pure 3D counterpart (MAPbI₃ ). This article is part of the Special Collection on "Perovskite Materials and Devices". Read the full text of the article at 10.1002/cplu.202000777.