Electronic transition responsible for size-dependent photoluminescence of colloidal CuInS2 quantum dots

Colloidal CuInS2 quantum dots with an average size of 2.9-4.1 nm were synthesized by the one-pot heating of an organometallic solution. The size-dependent optical gaps and photoluminescence (PL) emission energies were analyzed based on the finite-depth well effective mass approximation. The PL emission was attributed to the recombination of electrons in the donor level and holes in the quantized hole state. Indium atom defects at copper sites or sulfur vacancies were proposed to be the defects acting as donors at similar to 0.1 eV below the conduction band.