Stable and luminescent Cu-doped ZnSe nanocrystals (NCs) were synthesized in organic solvents with octadecylamine (ODA) as the capping ligand and characterized using a combination of optical and structural characterization techniques. Successful doping was achieved by adding Cu during the growth phase of the NCs when their size was ∼4 nm. The appearance of red-shifted, intense photoluminescence (PL) peak with doping indicates the incorporation of Cu in the NCs, and stability of dopant emission infers the internal doping of NCs. Extended X-ray absorption fine structure (EXAFS) studies revealed that Cu is surrounded by four neighbors in the lattice but is very close to the NC surface and gets oxidized when NCs are precipitated from the solution. For the undoped sample, time-resolved PL studies using time-correlated single photon counting (TCSPC) reveal the luminescence decay lifetimes of about 1.1, 12, and 60 ns that we attribute to near-bandedge, shallow trap (ST) state, and deep trap (DT) state emissions, respectively. In addition to these decay components, the Cu-doped sample was found to have a long-lived component with a lifetime of 630 ns. Luminescence decay lifetimes of near-bandedge and ST state emissions were slightly shortened by doping (1 and 10 ns, respectively), suggesting that the Cu dopant competes with these states in trapping the charge carriers from the conduction band (CB) or near-bandedge states. However, the presence of Cu was found to increase the lifetime of DT states from 60 to 100 ns probably due to a decrease in coupling of electron and hole states involved in this emission upon Cu doping. Synthesis of such stable, doped samples along with a better understanding of charge carrier dynamics is significant for emerging optical applications of these NCs.

Fluorescent, organically soluble Cu and Br codoped ZnS nanocrystals (NCs) were synthesized and characterized for the potential application of AC electroluminescent (EL) lighting devices. The doped NCs were optically characterized using UV–vis, photoluminescence (PL), Fourier transform infrared (FTIR), and time-resolved PL spectroscopy, and structurally characterized using transmission electron microscopy (TEM) and extended X-ray absorption fine structure (EXAFS). The PL emission of the undoped ZnS NCs upon λex = 280 nm was broad with a peak in the range of 450–470 nm, depending on the preparation of the NCs. Upon doping ZnS NCs with Cu, the PL emission was increased slightly with little change in spectral features. When Br dopant was added in addition to Cu, the codoped ZnS NCs showed much stronger PL emission (∼5 × ) compared to the undoped or Cu-doped sample. In conjunction with time-resolved PL results, this enhanced emission is attributed to a donor–acceptor (D–A) type of transition, between the Br electron trap and Cu hole trap, respectively. The time-resolved PL studies provide important information about the lifetimes of associated states and help to gain new insights into the nature of the states involved in the observed PL. The EXAFS data reveal that Br is clearly incorporated into the NCs. Increased disorder around Br with increasing Cu suggests that the Br is located near Cu within the ZnS lattice. This study demonstrates successful Cu-doping of ZnS NCs by using a halogen coactivator, for the first time, in an organic solvent. Organic soluble systems have proven more advantageous for preparation of high-quality thin films.

Experimental and theoretical investigation of the electronic structure of Cu2O and CuO thin films on Cu(110) using x-ray photoelectron and absorption spectroscopy Chalcocite (Cu 2 S) has been deposited via pulsed chemical vapor deposition (PCVD) into a porous TiO 2 matrix using hydrogen sulfide and a metal-organic precursor. The precursor used is similar to the more common Cu(hfac)(tmvs) precursor, but it is fluorine free and exhibits increased thermal stability. The simultaneous exposure of the substrate to the copper precursor and hydrogen sulfide resulted in nonuniform Cu 2 S films with a temperature independent deposition rate implying gas phase reaction kinetics. The exposure of mesoporous TiO 2 and planar ZnO to alternating cycles of the copper precursor and hydrogen sulfide resulted in a PCVD film that penetrated fully into the porous TiO 2 layer with a constant deposition rate of 0.08 nm/cycle over a temperature range of 150-400 C. The chalcocite (Cu 2 S) stoichiometry was confirmed with extended x-ray absorption fine structure measurements (EXAFS) and x-ray photoelectron spectroscopy. Calculations of the EXAFS spectrum for different Cu x S phases show that EXAFS is sensitive to the different phase stoichiometries. Optical absorption measurements of CVD thin films using photothermal deflection spectroscopy show the presence of a metallic copper-poor phase for gas phase nucleated films less than 100 nm thick and a copper-rich semiconducting phase for thicknesses greater than 100 nm with a direct band gap of 1.8 eV and an indirect bandgap of 1.2 eV.