  Hitting hard on the binary halides yields in the formation of Cs2[AgIn]Br6.
The lead-free double perovskite marks, although not usable itself, a further
step forward in finding sustainable and durable perovskite materials for
photovoltaic applications. Cs2[AgIn]Br6 is one of the prominent examples of
double perovskites materials that have been suggested to circumvent the use of
lead compounds in perovskite solar cells. We herein report the successful
synthesis of the material using a mechanochemical approach. It crystallizes in
an elpasolite-type structure, an ordered perovskite superstructure, with a cell
parameter of a = 11.00 {\AA}. However, the compound exhibits a relatively large
optical bandgap of 2.36 eV and is unstable under illumination, which impedes
its use as solar absorber material at this early stage. Still, substitution of
lead and the potential of this synthesis method are promising as well as the
fruitful combination of theoretical considerations with experimental materials
discovery.
