Phase-Controlled Synthesis of Alloyed (CdS)x(CuInS2)1−x Nanocrystals with Tunable Band Gap

Phase and band gap engineering of (CdS)x(CuInS2)1−xnanomaterials is critical for their potential applications in photovoltaics and photocatalysis, yet it remains a challenge. Here, we report a precursor-mediated colloidal method for phase-control synthesis of alloyed (CdS)x(CuInS2)1−xnanocrystals with tunable band gap. When CuCl, InCl3, and Cd(AC)2·2H2O are used as the respective cation sources, wurtzite-structured alloyed (CdS)x(CuInS2)1−xnanocrystals can be synthesized with a tunable optical band gap ranging from 1.56 to 2.45 eV by directly controlling the molar ratio of the Cd precursor. Moreover, using Cu(S2CNEt2)2, In(S2CNEt2)3, and Cd(S2CNEt2)2as cation sources results in alloyed (CdS)x(CuInS2)1−xnanocrystals with a zinc-blende structure, demonstrating that the optical band gap of these nanocrystals can be compositionally tuned from 1.50 to 1.84 eV through precisely adjusting the molar ratio of Cd precursor. The results were validated through a comprehensive characterization approach employing XRD, TEM, HRTEM, STEM-EDS, XPS, UV-vis-NIR absorption spectroscopy, and Mott–Schottky analysis.