Photoinduced carrier dynamics of nearly stoichiometric oleylamine-protected copper indium sulfide nanoparticles and nanodisks

Copper indium sulfide (CuInS₂) nanocrystals (NCs) are nontoxic and cost-effective, making them attractive for use in highly efficient solar cells. However, direct observations of the photoinduced carrier dynamics of CuInS₂ NCs to examine the relationship between carrier dynamics and structural parameters with the aim of optimizing NC properties for specific applications are limited. Here, we synthesized nearly stoichiometric oleylamine-protected CuInS₂ NCs using two convenient one-pot methods to produce CuInS₂ nanoparticles and nanodisks. Transient absorption measurements using femtosecond laser flash photolysis revealed that the use of oleylamine as a protecting ligand leads to the formation of vacancy-doped NCs. The rapid decay of the photogenerated excitons in the oleylamine-protected NCs was not sensitive to the crystal structure or shape of NCs, and could be explained by defect trapping and energy transfer to the hole-based localized surface plasmon resonance in the oleylamine-protected NCs. Our results confirm that careful selection of a protecting ligand is important to obtain CuInS₂ NCs with optimized properties for particular applications.