Single crystal growth by self-flux method of the mixed valence gold halides Cs2[AuIX2][AuIIIX4] (X=Br,I)

High quality single crystals of Cs2Au2X6 (X = Br,l) were grown using a ternary self-flux method. Structural refinements based on single crystal X-ray diffraction measurements show that both materials have a distorted perovskite structure belonging to the I4/mmm space group with full site occupancy. Transport measurements reveal a large bandgap of 550 +/- 100 meV for Cs2Au2I6 and 520 +/- 80 meV for Cs2Au2Br6. Initial attempts at chemical substitution are described. Published by Elsevier B.V.