Ultrafast dynamics and ultrasensitive single particle spectroscopy of optically robust core/alloy shell semiconductor quantum dots

• Published in: Physical chemistry chemical physics : PCCP 2022-04, Vol.24 (15), p.8578-859
• Main Authors: Roy, Debjit, De, Chayan K, Ghosh, Swarnali, Mukherjee, Soumen, Mandal, Saptarshi, Mandal, Prasun K
• Format: Article
• Language: English
• Subjects: Bleaching; Bluing; Cadmium selenides; Core-shell structure; Current carriers; Decay rate; Dynamics; Excitons; Hot electrons; Nucleation; Quantum dots; Surface tension; Synthesis; Thermalization (energy absorption); Time constant; Trapping
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d1cp05780d

A "one-pot one-step" synthesis method of Core/Alloy Shell (CAS) quantum dots (QDs) offers the scope of large scale synthesis in a less time consuming, more economical, highly reproducible and high-throughput manner in comparison to "multi-pot multi-step" synthesis for Core/Shell (CS) QDs. Rapid initial nucleation, and smooth & uniform shell growth lead to the formation of a compositionally-gradient alloyed hetero-structure with very significantly reduced interfacial trap density in CAS QDs. Thus, interfacial strain gets reduced in a much smoother manner leading to enhanced confinement for the photo-generated charge carriers in CAS QDs. Convincing proof of alloy-shelling for a CAS QD has been provided from HRTEM images at the single particle level. The band gap could be tuned as a function of composition, temperature, reactivity difference of precursors, etc. and a high PLQY and improved photochemical stability could be achieved for a small sized CAS QD. From the ultrafast exciton dynamics in CdSe and InP CAS QDs, it has been shown that (a) the hot exciton thermalization/relaxation happens in