Absolute Photoluminescence Quantum Yields of IR-26 Dye, PbS, and PbSe Quantum Dots
In this study, we have directly measured the photoluminescence quantum yield (Φ PL ) of IR-26 at a range of concentrations and the Φ PL of PbS and PbSe QDs for a range of sizes. We find that the Φ PL of IR-26 has a weak concentration dependence due to reabsorption, with a Φ PL of 0.048 ± 0.002% for low concentrations, lower than previous reports by a full order of magnitude. We also find that there is a dramatic size dependence for both PbS and PbSe QDs, with the smallest dots exhibiting a Φ PL in excess of 60%, while larger dots fall below 3%. A model, including nonradiative transition between electronic states and energy transfer to ligand vibrations, appears to explain this size dependence. These findings provide both a better characterization of photoluminescence for near-infrared emitters and some insight into how improved QDs can be developed.