Abstract
Recently, metal halide perovskite solar cells (PSCs) of the general formular ABX(3) where A is a monovalent cation, that is, methylammonium (MA) CH3NH3+center dot, formamidinium CH2(NH2)(2)(+), Cs+, or Rb+, B stands for Pb(II) or Sn(II), and X for iodide or bromide have achieved solar to electric power conversion efficiencies (PCEs) above 22%, exceeding the efficiency of the present market leader polycrystalline silicon while using 1000 times less light harvesting material and simple solution processing for their fabrication. The top performing devices all employ formulations containing a mixture of up to four A cations and iodide as well as a small fraction of bromide as anion, whose emergence will be described in this Commentary. Apart from leading the current PV efficiency race, these new perovskite materials exhibit intense electroluminescence and an extraordinarily high stability under heat and light stress.