Guolong Tan

Abstract:

Composition-tunable ternary semiconductor nanocrystals (NCs) are very important materials for light harvesting as well as remote sensing and detecting in the infrared (IR) wavelength region. They are, however, almost exclusively prepared by wet chemical routes which lead to surface-capped nanoparticles. The surface capping molecules could shift their absorption peaks from mid-IR to near IR wavelength region. Surface clean binary and ternary nanocrystals (NCs) would demonstrate intrinsic optical spectrum in the entire wavelength region. Herein, we will present the preparation of tens of grams of surface clean binary and ternary semiconductor nanocrystals (such as CdS, CdSe, CdTe, CdSeS, CdZnS, CdPbS, CuSbS2) using physical mechanical alloying (MA) process. The resulting nanocrystals have average sizes smaller than 9 nm, are chemically homogenous, show lattice contraction with chemical composition and a variable band gap-composition relationship, which enable us to continuously and precisely tune the band gap energies of ternary semiconductor nanocrystals from ultra violet region, visible wavelength region to mid-IR region, and even to far-IR region. The smallest bang gap energy of one specific semiconductor nanocrystals extends to far infra-red wave length region, which reaches as small as 25 um. We will show such full optical spectrum with two free exciton peaks locating just below the bottom of the conduction band at room temperature. These semiconductor nanocrystals have great potential application for light harvesting in solar cells and hydrogen generation from water splitting.