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Synthesis and characterization of III-V colloidal semiconductor nanocrystals doped with rare-earth ions

Abstract : This thesis focuses on the synthesis of III-V colloidal semiconductor nanocrystals (NCs) doped with rare earth (RE) ions by various synthetic methods. Nearly monodisperse series of InP and In(Zn)P core NCs as well as of strongly luminescent InP/ZnS and In(Zn)P/ZnS core/shell NCs were successfully synthesized by reaction of the In precursor (indium myristate) with different phosphorous precursors such as yellow phosphorous, PH3 gas or P(TMS)3 in the non-coordinating solvent 1-octadecene. The prepared NCs were characterized by powder XRD, TEM, EDX, XRF, UV-vis absorption and steady-state (SSPL) as well as time-resolved photoluminescence (TRPL) spectroscopy. Alloy In(Zn)P and In(Zn)P/ZnS QDs were synthesized in a heating-up one-pot method by adding zinc stearate during the nucleation and growth process of InP NCs. The alloy In(Zn)P/ZnS QDs showed high PL quantum yield (QY) up to 70% and their emission could easily be tuned in the range from 480 to 590 nm (FWHM: 50 nm) by varying the Zn2+:In3+ molar ratio and the reaction temperature. The high PL QY is rationalized by band-edge fluctuation occurring in the In(Zn)P alloy structure, which contributes to the confinement of photoexcited carriers. Eu-doped In(Zn)P/ZnS NCs were successfully synthesized in a three-step one-pot method, namely (step 1) synthesis of the In(Zn)P host NCs; (step 2) Eu-dopant growth; (step 3) synthesis of the outer ZnS shell. Complementary optical measurements - absorption, PL, PLE, phosphorescence and TRPL spectroscopy - confirmed the successful doping of the In(Zn)P/ZnS NCs with Eu and revealed resonant energy transfer between the In(Zn)P host and the Eu3+ guest ions. Finally, we have studied the influence of the surrounding environment on the optical characteristics of alloy In(Zn)P/ZnS QDs by comparing close-packed NC films and colloidal solutions. The SSPL spectra from the close-packed In(Zn)P/ZnS NCs are peaking at shorter wavelengths in comparison with those taken from the colloidal ones. In addition, TRPL studies show that the close-packed In(Zn)P/ZnS NCs possess a shorter luminescence decay time and a strongly increased spectral shift with the delay time from the excitation moment in comparison with the colloidal ones. Förster resonance energy transfer and/or excited charge-carrier transfer between the In(Zn)P/ZnS NCs are the main reasons for the observed behavior. The evidence of charge-carrier transfer in close-packed layers of In(Zn)P/ZnS QDs is very important for their integration into optoelectronic devices, such as QD LEDs or LEFETs.
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Submitted on : Monday, September 26, 2011 - 2:08:56 PM
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  • HAL Id : tel-00626513, version 1



Thuy Dieu Thi Ung. Synthesis and characterization of III-V colloidal semiconductor nanocrystals doped with rare-earth ions. Chemical Sciences. Institute of Materials Science, VAST Vietnam, 2010. English. ⟨NNT : ⟩. ⟨tel-00626513⟩



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