2, The University of Texas at Dallas, Dallas, Texas, United States
Near-infrared (NIR) PbS nanocrystal quantum dots (QDs) have immense potential in realizing many technological applications ranging from photovoltaic devices to biological labeling. However, their application in practical devices or in challenging environments, respectively, has been limited by instability in photoluminescence quantum yield (QY) and peak position as a result of surface oxidation. Here, we describe a combination of cation exchange and successive ionic layer adsorption and reaction (SILAR) methods to synthesize stable NIR PbS/CdS/CdS core/shell/shell “giant” QDs (gQDs). The thick shell affords significantly increased stability under ambient conditions as observed in time-dependent absorption and QY studies of ensembles of PbS/CdS/CdS gQDs compared to thinshell variant. Furthermore, we describe the first investigation of PbS QDs at the single dot level using conventional detectors, including blinking statistics as a function of shell thickness. Finally, we show that these newly stabilized PbS QDs can be used to construct efficient solid-state down conversion NIR light emitting devices, for which, like blinking suppression, lifetime operational stability is shell thickness dependent. In this way, we show a clear correlation between nanoscale structure and both single dot properties and device performance.