A comprehensive understanding of failure modes of solar photovoltaic (PV) modules is key to extending their operational lifetime in the field. In this review, first, specific failure modes associated with mature PV technologies, such as crystalline silicon (c‐Si), copper indium gallium selenide (CIGS) and cadmium telluride (CdTe), are framed by sources of specific failure modes, their development from the early‐developmental stages onwards and their impact upon long term performance of PV modules. These failure modes are sorted by both PV technology and location of occurrence in PV modules, such as substrate, encapsulant, front and rear electrode, absorber and interlayers. The second part of the review is focused on emerging PV technologies, such as perovskites solar cells, dye sensitised and organic PVs, where due to their low to medium technology readiness levels, specific long‐term degradation mechanisms have not fully emerged, and most mechanisms are only partially understood. However, an in‐depth summary of the known stability challenges associated with each emerging PV technology is presented. Finally, in this paper, lessons learned from mature PV technologies are reviewed, and considerations are given in to how these might be applied to the further development of emerging technologies. Namely, any emerging PV technology must eventually pass industry‐standard qualification tests, while warranties for the lifetime of modern c‐Si‐based modules might be extended beyond the existing warranted life of 25 years.

The preparation, crystal structure and optical absorption spectra of [H₃N(CH₂)₆NH₃]PbX₄ (X = I, Br, Cl) and similar compounds based on Sn are described. The compounds [H₃N(CH₂)₆NH₃]PbX₄ consist of ordered perovskite sheets of the corresponding-corner sharing PbX₆ octahedra, which alternate with the H₃N(CH₂)₆NH₃ sheets. The excitonic peaks in the optical absorption spectra of these compounds occur at shorter wavelengths than those of the corresponding compounds with the formula [C₆H₅CH₂CH₂NH₃]₂MX₄.

The preparation, crystal structures and optical absorption spectra of [H₃N(CH₂)₆NH₃]BiX₅ (X= I, Cl) and [H₃N(CH₂)₆NH₃]SbX₅ (X =I, Br) are reported. The anions of the compounds consist of MX₆-octahedra (M =Bi, Sb) sharing cisvertices in one-dimensional zig-zag chains. Because of their one-dimensional character, a blue shift of the excitonic absorption bands, in com parison to those of higher dim ensionality systems (MX₃), is observed.