| Outline of Annual Research Achievements |
The research accomplished defect-free, highly luminescent and nonblinking halide perovskite quantum dots (QDs, <7 nm edge lengths/diameters), nanocrystals (PNCs, 9~12 nm edge lengths) and microcrystals (PMCs, >5 micrometer edge length cubes, plates, and rods). Perovskite samples were CsPbBr3 PNCs, and MAPbBr3 (MA=methylammonium) QDs, PNCs and PMCs. The as-synthesized samples showed <30% photoluminescence (PL) quantum yields (QYs) with short PL lifetime values and PL blinking. The low PL QYs, short PL lifetimes, and PL blinking suggested a large defect density. First A and B site cation vacancies were filled by supplementing cesium oleate or Pb-oleate to CsPbBr3 and MaPbBr3 PNCs. There was no change to the PL QY. However, the PL QY was increased to the champion 100% by applying NaBr to CsPbBr3 PNCs, which was 78 to 82% for by applying MABr/MAI to MAPbBr3/MAPbI3. Furthermore, the PL intensities of MAPbBr3 PMCs were increased 5-7-fold by MABr. In all these cases, the PL lifetime was appreciably increased and PL blinking was completely suppressed, showing suppression of defect-assisted nonradiative recombination. Nevertheless, electron acceptors (fullerene/TiO2/cyanobenzenes) and electron donors (aliphatic amines, amine dendrimers, and polyamine-poly carboxylic acid conjugates) quenched the PL. Like the PL QY, intensity and lifetime increases with NaBr/MaBr/MAI addition, the research accomplished electroluminescence (EL) intensity increase and EL blinking suppression for MAPbBr3 PMCs, conformed by measurements using a newly designed single-particle EL instrument.
|
