Recent Progress in the Solution-Based Sequential Deposition of Planar Perovskite Solar Cells

Hybrid organic-inorganic metal halide perovskites have probably become the most famous and prospective class of materials for photovoltaic application in the past decade. The extremely fast increase of certified power conversion efficiencies, from 3.8 to 22.7% in less than seven years, encourages researchers around the globe and indicates the materials advantageous optoelectronic properties. The most important properties for future commercialization have turned out to be the low cost of precursor materials and the simplicity of solution processability. This article reviews the latest advancements in the solution-based sequential deposition of planar perovskite absorber layers, which show promise to be multifaceted, reproducible, and controllable. Strong research interest has recently been devoted to the optimization of the surface coverage and morphology, both of which considerably influence the photovoltaic performance. Herein, we first concentrate on the deposition of lead-containing precursors from typical polar solvents and review modifications via additive incorporation and pre-/post-treatment. Afterward, innovative methods for the conversion reaction in the usually alcoholic solvent are summarized, and the influence on the final crystal morphology is highlighted. We conclude with a short discussion about future directions and challenges.