**2.1. Deposition techniques of inorganic–organic solar cells materials**

The deposition technique is a quite important issue for perovskites studies, because many investigations and possible usages of organic-inorganic perovskite hybrids rely on the accessibility of simple and accurate thin film deposition method. But deposition of perovskite materials is often challenging because of the different chemical and physical property of the inorganic and organic portions [26]. For example, organic materials trend to be soluble in various solvents than inorganic section, this is causing chemical precursor solution preparation techniques (e.g., spin coating and dip coating) usually infeasible. For those reasons where the organic-inorganic hybrid is soluble, solution techniques are sometimes not suitable because of adverse wetting characteristics of some substrates, make deposition inhomogeneous. With respect to vacuum evaporation methods, the gradual heating of organic-inorganic compounds typically results in the decomposition or dissociation of the organic component at a lower temperature or rapidly than that needed for evaporation of the metal halide component. Despite these evident difficulties, organic-inorganic perovskites represent a number of significant opportunities for thin film deposition or crystal growth of organic-inorganic hybrid perovskites, such as two-step dipping technique, spin coating, stamping, Langmuir-Blodgett (LB), two source thermal evaporation, solution evaporation and so on, which make possible the applications of perovskites as organic-inorganic electronic or photonic devices [27,28]. This section will offered a selected compilation of recent progress in this topic, demonstrating that a number of simple and effective methods can be utilized for the deposition of this considerable class of materials.
