- The solution-based thermolysis of the organometallic single-source precursors [(iPr3PCu) 4 (MeGa) 4S6](1) and [(iPr3PCu) 4 (MeIn) 4Se6](2) is investigated. Multinary semiconductor nanocrystals with sizes in the range of 3–10 nm are obtained by a simple heating-up process in a solvent mixture of long-chain alkyl thiols and amines. The thiols also serve as a sulfur source and capping ligand for the nanoparticles. By mixing 1 and 2, nanocrystal compositions in the range from CuGaS2 to CuInSSe are accessible. Surface passivation of the nanocrystals with ZnS results in high stability and bright photoluminescence (PL). PL maxima are observed in the spectral range between 600 and 800 nm, depending on the size and composition of the nanocrystals. The highest PL quantum yields exceed 50% and are observed for a gallium to indium ratio of 1: 5.