| 초록 |
Core/shell heterostructures, passivating emissive core with wide band gap shell, have become key strategy for stable and efficient quantum dot (QD) emitters. In general, the shell thickness merely ranges within 1 – 3 nm due to its intrinsic “misfit” to the core; lattice mismatch develops the strain at their interface and inordinate shell growth produces crystal defects lowering photoluminescence (PL) QY. In this study, we demonstrate a counter example on this general awareness, which allows for realizing unity PL QY by increasing compressive strain. When we grew thick CdZnSe shell on CdSe core, we observed gradual degradation of PL QY. Surprisingly, introduction of ZnSeS outer shell intensifying compressive strain recovered PL QY of QDs up to ~100%. Based on spectrally-resolved PL decay, PL excitation spectra and elastic continuum model, we conclude that the compressive strain raises the emissive states of core against hole defects, so deactivates trap-involved nonradiative decay. |
