Spectral and Temporal Optical Behavior of Blue-, Green-, Orange-, and Red-Emitting CdSe-Based Core/Gradient Alloy Shell/Shell Quantum Dots: Ensemble and Single-Particle Investigation Results

Abstract

Highly luminescent (photoluminescence quantum yield (PLQY) as high as 96%) CdSe-based core/gradient alloy shell/shell (CGASS) quantum dots (QDs) have been synthesized in “one pot” using the reactivity difference between Cd and Zn precursors and Se and S precursors. This procedure is highly reproducible and quite useful for large-scale synthesis. Upon photoexcitation these QDs show a multiexponential excited state decay behavior. Interestingly, with the growth of the shell the overall PL decay gets faster. All the decay traces have been fitted well with a three exponential decay function. Fitted decay traces reveal three different time constants, a faster one of 1–4 ns, moderate one of 13–16 ns, and slower one >25 ns. With the growth of the shell, the amplitude for the moderate time constant increases, and that of the slow time constant decreases consistently. The variation of PLQY could be correlated with the variation of amplitude of the moderate time constant. Slow and moderate time constants have been ...