Polymorphic Graphene-like Cuprous Germanosulfides with a High Cu-to-Ge Ratio and Low Band Gap

Metal chalcogenides based on heterometallic
Ge–Cu–S
offer dual attractive features of lattice stabilization by high-valent
Ge4+ and band gap engineering into solar region by low-valent
Cu+. Herein via cationic amine intercalation, we present
three new copper-rich materials with the Cu-to-Ge ratio as high as
3. Two different patterns of Cu–Ge–S distribution could
be achieved within each honeycomb sheet. The decoration of such honeycomb
sheet by −Cu−S− chain or self-coupling between
two honeycomb sheets leads to two layer configurations with different
thickness and band gaps. The band gap of these new phases (2.06–2.30
eV), tuned by the layer thickness and the Cu/Ge ratio, represents
a significant red shift over known Cu–Ge–S phases with
lower Cu/Ge ratios.