Development of Non-Toxic Quantum Dots for Flexible Display Applications
Final rept. 9 Aug 2011-8 Aug 2013
HANNAM UNIV DAEJEON (KOREA)
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In order to achieve nanocrystals NC with stable and high photoluminescence PL and light harvesting efficiency LHE, rare earth RE elements doped coreshell CS type semiconductors NC quantum dots QDs of group III-V elements were attempted with group II-VI element shell materials. An industrially adaptable low temperature ammine-ligands based process was chosen initially for the synthesis. Color control was achieved by tuning the size of the NCs. QDs having photoluminescence from infrared IR to blue were successfully synthesized. Quantum yield QY of these materials were attempted to increase by tuning the shell architecture. PL enhancement was observed with multiple shell growth indicating the inappropriate electronic bandgap and band alignment and surface lattice mismatch parameters for InPZnS binary CS system. A coreshellshell CSS structure was attempted to overcome this lattice mismatch issue. Improvisation in efficiency was expected by converting them to upconverting nanoparticles NPs. Doping with suitable IIB Zn, VIIB Mn and RE elements Ce, Er can make them upconverting NPs free from environmental issue. Doping also could improve their thermal stability in display devices and increase the QY. Upconverting NPs are advantageous because in their hybrid photovoltaic devices they can produce high QY at IR region where solar spectrum has the highest photon flux density and also it is the region where most of the other materials fail. Doping these NCs with RE elements exhibited increase the optical efficiency. To improve the interparticle charge transport, surface modified versions of these nanoparticles were synthesized by replacing organic capping ligands on chemically synthesized nanocrystals with metal-free inorganic S2- and HS- ions which provided colloidal stability for the NCs in polar solvents.
- Inorganic Chemistry
- Quantum Theory and Relativity