Colloidal Quantum dots
Novel colloidal quantum dots are comprised of an emitting cadmium/selenium core enclosed into a compositionally graded CdxZn1-xSe shell wherein the fraction of zinc versus cadmium increases towards the dot's periphery. Purposely "squashing" colloidal quantum dots throughout chemical synthesis generates a stable, “blink free” light emission that is similar to the lights produced by dots with more complex processes. New research at Los Alamos National Laboratory proposes that the strained colloidal quantum dots signify a feasible substitute to presently employed nanoscale light sources.
Victor Klimov, lead Los Alamos researcher on the project, said that in addition to displaying critically improved operation over traditional produced quantum dots, these new strained dots could offer unparalleled flexibility in handling their emission color. This in combination with the unusually narrow, 'sub-thermal' linewidth, and compatible with virtually any substrate. The new colloidal processing methods allows with nearly 100 percent emission quantum yields shown for a wide range of visible, infrared and ultraviolet wavelengths. This results to successful commercialization of quantum dot displays and TV sets.
The next frontier is exploration of colloidal quantum dots as single-particle, nanoscale light sources. In a new publication in the journal Nature Materials, Los Alamos researchers showed that spectral fluctuations in single-dot emission can be suppressed completely with the use of the method of "strain engineering”. The main approach is to combine in a core/shell motif two semiconductors with directionally asymmetric lattice mismatch which results in anisotropic compression of the emitting core. This modifies the structures of electronic states of a quantum dot and thereby its light emitting properties.
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