Direct Band Gap Mixed-Valence Organic–inorganic Gold Perovskite as Visible Light Absorbers

Lead-free halide
perovskite semiconductors are necessary due to
the atmospheric instability and lead toxicity associated with the
3D lead halide perovskites. However, a stable lead-free perovskite
with an ideal band gap (1.2–1.4 eV) for photovoltaics is still
missing. In this work, we synthesized organic–inorganic gold
halide double perovskites ((CH3NH3)2Au2X6, X =
Br, I) through a solution-processed route that offers an ideal direct
band gap for photovoltaic applications. Density functional theory
calculations confirm the direct nature of the band gap with reasonable
absorption coefficients in the visible range and excellent charge
transport properties. In addition, the Au-halide perovskites show
high chemical stability and photoresponse. These combined properties
demonstrate that Au-based halide perovskites can be a promising group
of compounds for optoelectronic applications.