Semiconductor nanostructures: Two dimensions are brighter

Semiconductors are brighter emitters of light when they are fabricated to be only tens to hundreds of atoms thick in one or more dimensions. Two-dimensional materials of this type, called quantum wells, make excellent lasers. Ithurria and colleagues report that nanoplatelets reminiscent of quantum wells are potentially better emitters because more atoms are recruited to capture and radiate light coherently. Nanoplatelets of semiconductors such as cadmium selenide are formed in solution by an unusual process whereby seed nanocrystals aggregate into rafts that eventually fuse into a two-dimensional sheet. The high propensity to absorb, and emit light termed giant oscillator strength (GOST) is related to the interaction between electrons and light in matter. Molecular J-aggregates' exceptionally sharp absorption spectrum and absorption strength that cemented these somewhat complex structures as premium dyes for photographic media.