Controllable Synthesis of Bandgap‐Tunable CuS x Se 1− x Nanoplate Alloys

Composition engineering is an important approach for modulating the physical properties of alloyed semiconductors. In this work, ternary CuS x Se 1− x nanoplates over the entire composition range of 0≤ x ≤1 have been controllably synthesized by means of a simple aqueous solution method at low temperature (90 °C). Reaction of Cu 2+ cations with polysulfide/‐selenide ((S n Se m ) 2− ) anions rather than independent S n 2− and Se m 2− anions is responsible for the low‐temperature and rapid synthesis of CuS x Se 1− x alloys, and leads to higher S/Se ratios in the alloys than that in reactants owing to different dissociation energies of the Se−Se and the S−S bonds. The lattice parameters ‘ a ’ and ‘ c ’ of the hexagonal CuS x Se 1− x alloys decrease linearly, whereas the direct bandgaps increase quadratically along with the S content. Direct bandgaps of the alloys can be tuned over a wide range from 1.64 to 2.19 eV. Raman peaks of the S−Se stretching mode are observed, thus further confirming formation of the alloyed CuS x Se 1− x phase.