The compound (Et3S)[Ag4I5], 1, is readily synthesized from room-temperature, ionic-liquid media and displays a complex network structure of Ag6I6 cages with Ag22+ pairs forming 1D-chains linked into layers distinctly separate from the disordered sulphonium cations. The compound should be regarded as a large-bandgap semiconductor, but its significant structural voids qualify the compound a candidate for optoelectronic applications through the inclusion of suitable guest molecules.