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Growth of InZnP/ZnS core/shell quantum dots with wide-range and refined tunable photoluminescence wavelengths
摘要： Owing to their environmental-friend characteristic, InP-based quantum dots (QDs) showed great potential in various fields as an alternative to Cd-based QDs. However, the current mainstream synthesis method, (TMS)3P-based injection method, still faces many challenges, such as high cost of (TMS)3P and complex temperature control. In contrast, solvent-thermal method is considered to be more feasible and reproducible. Despite its potential advantages, little has been done to understand how the precursors influence the synthesis of InP QDs using the solvent-thermal method. In this research, InZnP/ZnS QDs are synthesized with usage of practical phosphorus precursors (DEA)3P or (DMA)3P. Through the feasible regulation of zinc, indium, phosphorus and sulfur precursors, the band gap of the QDs can be widely and accurately tuned, and a much wider photoluminescence wavelength ranging from 484 nm to 651 nm can be achieved. Furthermore, InI3 and InBr3 contribute to the blue-shift of PL wavelengths, and the combination of (DEA)3P, (DMA)3P, n-DDT and t-DDT refine the PL wavelength with a small tuning gap of 5 nm.
关键词： photoluminescence,precursors,solvent-thermal method,InP-based quantum dots,tuning
更新于2025-09-19 17:13:59
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Ultrafast Dynamics and Ultrasensitive Single-Particle Intermittency in Small-Sized Toxic Metal Free InP Based Core/Alloy-shell/Shell Quantum Dots: Excitation Wavelength Dependency Towards Variation of PLQY
摘要： Observation of strong deviation of photoluminescence excitation curve from absorption curve specially at lower wavelength range, below 450 nm in case of small sized toxic metal free InP based core-alloy-shell quantum dots hints towards interesting exciton dynamics. PL quantum yield (PLQY) has been observed to be dependent on the excitation wavelength. Monitoring the bleach dynamics employing femtosecond ultrafast pump-probe technique it could be shown that the rise-time increases with decrease in pump excitation wavelength from 100 fs for 550 nm excitation to 220 fs for 430 nm pump/excitation. Therefore exciton cooling takes longer time for lower wavelength excitation and thus the exciton becomes more prone to get trapped. About two fold enhancement in magnitude of normalized bleach signal at the band edge (~0.1 (for 430nm excitation) to ~0.2 (for 550nm excitation)) following exciton relaxation has been observed. Thus, in comparison to lower wavelength excitation, for near band-edge pump/excitation there is higher probability of radiative exciton recombination, therefore increasing PLQY. Hot exciton trapping dynamics has been noted to be occurring at a timescale ~750 fs. From ultra-sensitive single particle measurement, magnitude of power-law exponent for both ON and OFF events remain similar to each other and the magnitude remains unaltered for different excitation wavelengths, (405 nm to 568 nm). As long as 100 s ON event could be observed making this InP based non-toxic QD quite suitable for single particle tracking etc. Interestingly, ON event truncation time has been found to increase from 6s to 16s and OFF event truncation time has been found to decrease from 11s to 5.5s, thereby exciton detrapping rate / trapping rate increases from 0.5 to nearly 3 on going from 405 nm to 568 nm excitation. Thus, as the trapping gets suppressed and detrapping gets enhanced, PLQY gets enhanced. The extent of relative decrease of PLQY value with increase in excitation energy above band-edge has been observed to be much more pronounced in CdSe based CAS QD than InP based CAS QD.
关键词： ultrafast dynamics,photoluminescence quantum yield,excitation wavelength dependency,InP based quantum dots,single-particle intermittency
更新于2025-09-11 14:15:04