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Perovskite solar cells (PSCs) are one of the most promising photovoltaic technologies undergoing rapid developments. PSC efficiency has reached 25.2% in only seven years, which is close to the record efficiency of silicon solar cells. In addition, the use of PSCs in tandem solar cells either in the 4-terminal or monolithic configuration, can lead to a significant increase conversion efficiency. However, the stability and the scalability are the main issues that still hinder the commercialization of the perovskite technology.The present review focusses on the recent development in perovskite solar cells materials, cell architectures and fabrication methods and their effect on the conversion efficiency and stability of the devices. In addition, solutions proposed to overcome the main challenges and to make tandem solar cells are discussed.

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Thin films of CuInTe 2 were grown by flash evaporation. The influence of the substrate temperature T s during film deposition on the properties of the thin films was examined. CuInTe 2 films were structurally characterized by the grazing incidence x-ray diffraction (GIXD) technique. Investigation by this technique demonstrates that the surface of thin films of CuInTe 2 prepared by flash evaporation at T s ≥ 100 • C exhibits the chalcopyrite structure with additional binary compounds in the surface. However, in the volume the films exhibit the chalcopyrite structure only; no foreign phases were observed. X-ray reflectometry was utilized to evaluate the critical reflection angle β c of CuInTe 2 (β CuInTe2 c ≈ 0.32 •) which permitted us to calculate the density of the films to be ρ ≈ 6 g cm −3. The evaporated films were p type and the films deposited at T s = 100 • C had a resistivity in the range 0.3-2 cm. From optical measurements we have determined the optical energy gap E g ≈ 0.94 eV and the effective reduced mass m * r ≈ 0.07m e .