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 CuInS2NCs using two convenient onepot 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.