Intensive development of solution deposition methods for perovskite solar cell fabrication requires rational optimization of existing methods and search for new effective solvents of different origin involved in key stages of the techniques. We propose a novel approach for rational solvent selection predetermining the character of their interaction with lead halide perovskites in terms of the analysis of donor numbers, dipole moments, and Hansen hydrogen bonding parameters. Experimental proof of the proposed approach provided a cutting-edge categorization of a wide range of possible solvents into four groups: inert, weak, strong, and AX-selective solvents. The resultant approach is a useful tool for perovskite solar cell fabrication.

Interaction of a copper electrode with methylammonium polyiodides is studied for the first time at the interfaces imitating hybrid perovskite solar cells. Along with a widely known copper corrosion productCuI, a new MACu2I3 phase is found. The presence of lead derivatives as well as reaction temperature are shown to have a strong influence on the resulting corrosion products. The interplay between lead- and copper-containing iodides allows revealing either realistic chemical corrosion pathways or possible practical benefits from CuI crystallization and perovskite recovery caused by the copper–iodine chemical “drain” in the system.

Layered hybrid halide perovskites (LHHPs) are an emerging type of semiconductor with a set of unique optoelectronic properties. However, the solution processing of high-quality LHHPs films with desired optical properties and phase composition is a challenging task, possibly due to the structural disorder in the LHHP phase. Nevertheless, there is still a lack of experimental evidence and understanding of the nature of the structural disorder in LHHPs and its influence on the optical properties of the material. In the current work, using 2D perovskites (C4H9NH3)2(CH3NH3)n−1PbnI3n+1 (further BA2MAn−1PbnI3n+1) with n = 1–4 as a model system, we demonstrate that deviations in LHHPs optical properties and X-ray diffraction occur due to the presence of continuous defects—Stacking Faults (SFs). Upon analyzing the experimental data and modeled XRD patterns of a possible set of stacking faults (SFs) in the BA2MAPb2I7 phase, we uncover the most plausible type of SFs, featured by the thickness variation within one perovskite slab. We also demonstrate the successful suppression of SFs formation by simple addition of BAI excess into BA2MAn−1PbnI3n+1 solutions.

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