Organic-inorganic hybrid perovskite materials (OHP, AMX₃, where A is organic or inorganic cation, M is metal cation, and X is a halogen anion) show considerable potential for solar cell and light-emitting diode applications. Metal halide perovskites have shown tremendous development in the photovoltaic technologies due to their intrinsic properties such as high absorption coefficient in the visible region, long carrier diffusion lengths, low cost of process ability. Since their first use for solar cell applications in 2009, they have demonstrated a fast expansion in the photovoltaic community, reaching nowadays a power conversion efficiency above 25%, which is highly competitive in comparison with CdTe (22.1%), CIGS (22.6%), and Si (25.4%). To overcome the weakness of OHP materials, such as material instability, many researchers are focusing on studying instability origins, stable compounds, defect structures, and multi-functional hole transport layer (good hole mobility and water protection). This work is proceeding to engineering optimization now. However, its fundamental properties in thin films such as defects, phonon dispersion, and electronic structure are not fully understood, which is why many researchers are still attempting to improve its weakness in actual devices.

In 2014, the first preparation of metal halide perovskites as luminescent colloidal nanocrystals revolutionized nanomaterials science. An impressive progress has been made during the last years, from fundamental research towards innovative applications of these nanomaterials in perovskite light-emitting devices (p-LED), lasing devices, photodetectors, and more recently, photocatalysis. Colloidal perovskite nanomaterials display outstanding optical and electronic properties, including broad absorption spectra and very narrow luminescence, high luminescent quantum yield and excellent band gap tunability depending on the cation or anion nature, size, and temperature. Moreover, the fine-tuning of the molar ratio between perovskite precursors and organic ligands allows the preparation of perovskite nanomaterials with different crystalline dimensionality and thus different optical properties. Several attempts to increase their stability towards humidity, heat, and light have been reported, but more investigations are necessary to reach practical applications.

This Special Issue aims to gather recent research on new inorganic or organic–inorganic hybrid perovskite materials, including their nanostructures, and not only the synthesis, crystal structure, characterization, and properties, but also their wide application from photovoltaic properties and performance.