The research and development of novel photovoltaic technologies is going through a golden era, thanks to the demonstration of remarkable efficiencies across a broad range of semiconductor classes and device architectures. In parallel with these developments, the opportunities for characterizing the structure of a semiconductor film in situ of a processing step have also increased, to the extent that in situ and in operando experiments are becoming readily accessible to researchers. These combined advances represent the subject matter of this article, wherein studies that improve our understanding of structure formation and evolution in perovskite and organic semiconductor films for innovative solar cells are reviewed. Although focus is placed on the dynamics of semiconductor film formation, the review also highlights recent research on environmental testing, a key component in the development of materials with high intrinsic stability.