High-Throughput Time-Resolved Photoluminescence Study of Composition- and Size-Selected Aqueous Ag-In-S Quantum Dots

Brightly luminescent, composition- and size-selected aqueous Ag-In-S (AIS) and Zn-diffused core/shell AIS/ZnS (ZAIS) quantum dots (QDs) were studied by high-throughput time-resolved photoluminescence (TRPL). Both QD size and QD composition effects on the photophysical properties of MS (ZAIS) were probed independently by using an automated high-throughput TRPL setup. Linear relationships were found between the average PL lifetimes of MS and ZAIS QDs and their respective bandgaps (E-g) indicating that the dynamics of the radiative recombination is governed mostly by the energy of the QD excited state irrespective of which factor is varied affecting the QD bandgap, i.e., their size or composition. The rate constants of radiative and nonradiative recombination were evaluated as a function of E-g forming continuous dependences for the entire MS and ZAIS QD families. The rate of nonradiative recombination increases steeply for smaller QDs with E-g > 2.2 eV for both core MS and core/shell ZAIS QDs, indicating that the interfacial electron transfer is the major contributor to the observed dependence. A strong decrease of the PL lifetime of MS (and ZAIS) QDs in dense QD films or QDs incorporated into polyvinylpyrrolidone films was observed as compared to colloidal solutions. A reversible character of this effect upon polymer film dissolution shows that such behavior originates from energy (or electron) transfers among the QDs brought into close contact in the films. This phenomenon is expected to be of significance for the application of ternary QDs as a light-harvesting material.

Automated summary

The study found that the photophysical properties of MS and ZAIS quantum dots are influenced by the size and composition of the QDs. Nonradiative recombination rate increases steeply for smaller QDs, indicating that interfacial electron transfer is a major contributor.