Spectroscopy

Quantum mechanics

Delocalized electron

Materials science

Absorption (acoustics)

Atomic physics

Photoluminescence

Photoexcitation

Band gap

Physics

Organic chemistry

Optics

Doping

Composite material

Auger effect

Excited state

Chemistry

Electron

Optoelectronics

Absorption spectroscopy

Ultrafast laser spectroscopy

ACS Nano

Colloidal Cu+-doped CdSe/CdS core/shell semiconductor nanocrystals (NCs) are investigated in their as-prepared and degenerately n-doped forms using time-resolved photoluminescence and transient-absorption spectroscopies. Photoluminescence from Cu+:CdSe/CdS NCs is dominated by recombination of delocalized conduction-band (CB) electrons with copper-localized holes. In addition to prominent bleaching of the first excitonic absorption feature, transient-absorption measurements show bleaching of the sub-bandgap copper-to-CB charge-transfer (MLCBCT) absorption band and also reveal a photoinduced midgap valence-band (VB)-to-copper charge-transfer (LVBMCT) absorption band that extends into the near-infrared, as predicted by recent computations. The photoluminescence of these NCs is substantially diminished upon introduction of excess CB electrons via photodoping. Time-resolved photoluminescence measurements reveal that the MLCBCT excited state is still formed upon photoexcitation of the n-doped Cu+:CdSe/CdS NCs, but its luminescence is quenched by a fast (picosecond) three-carrier trap-assisted Auger recombination process involving two CB electrons and one copper-bound hole.

Photodoping and Transient Spectroscopies of Copper-Doped CdSe/CdS Nanocrystals