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,I) 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.

► Single crystal growth of Au-halide mixed valence compounds by means of a ternary self-flux. ► Single crystal XRD measurements confirmed the previously determined crystal structure. ► Transport measurements reveal a band gap of 550 meV for Cs2Au2I6 and 520 meV for Cs2Au2Br6.