Retrograde solubility of formamidinium and methylammonium lead halide perovskites enabling rapid single crystal growth

Here we show the retrograde solubility of various hybrid perovskites through the correct choice of solvent(s) and report their solubility curves. Retrograde solubility enables to develop inverse temperature crystallization of FAPbX(3) (FA = HC(NH2)(2)(+), X = Br-/I-). FAPbI(3) crystals exhibit a 1.4 eV bandgap - considerably narrower than their polycrystalline counterparts.