Abstract
Perovskite solar cells based on methylammonium lead triiodide witnessed unprecedented progress after the seminal work of Miyasaka and co-workers in 2009, where they employed perovskite nanocrystals as sensitizers in a dye-sensitized solar-cell configuration. After key breakthroughs with solid-state perovskite photovoltaics in 2012, research efforts have grown exponentially, and several groups have demonstrated that the perovskite concomitantly acts as a light absorber and an electron and hole transporter in both mesoscopic networks and solid polycrystalline layers, where the perovskite layer can be deposited using a broad range of techniques. The methylammonium lead triiodide perovskite bandgap has been tuned by substituting various cations and anions. By optimizing the crystalline quality of the perovskite absorber and film formation by solvent engineering, a remarkable power-conversion efficiency of over 20% has been demonstrated, highlighting the exceptional photovoltaic properties of perovskite materials. The high efficiencies are due to a combination of long carrier lifetimes, substantial charge-carrier mobilities, and remarkably benign electronic defects. This issue highlights various deposition methods of the perovskite absorber, such as single-step, sequential, dual-source sublimation, and solution and sublimation processes, as well as hole-transporting-free and tandem perovskite solar cells.