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81.
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83.
PbTe colloidal nanocrystals: synthesis, characterization, and multiple exciton generation 总被引:1,自引:0,他引:1
Murphy JE Beard MC Norman AG Ahrenkiel SP Johnson JC Yu P Mićić OI Ellingson RJ Nozik AJ 《Journal of the American Chemical Society》2006,128(10):3241-3247
We report an alternative synthesis and the first optical characterization of colloidal PbTe nanocrystals (NCs). We have synthesized spherical PbTe NCs having a size distribution as low as 7%, ranging in diameter from 2.6 to 8.3 nm, with first exciton transitions tuned from 1009 to 2054 nm. The syntheses of colloidal cubic-like PbSe and PbTe NCs using a PbO "one-pot" approach are also reported. The photoluminescence quantum yield of PbTe spherical NCs was measured to be as high as 52 +/- 2%. We also report the first known observation of efficient multiple exciton generation (MEG) from single photons absorbed in PbTe NCs. Finally, we report calculated longitudinal and transverse Bohr radii for PbS, PbSe, and PbTe NCs to account for electronic band anisotropy. This is followed by a comparison of the differences in the electronic band structure and optical properties of these lead salts. 相似文献
84.
D-theory provides an alternative lattice regularization of the 2D CP(N-1) quantum field theory in which continuous classical fields emerge from the dimensional reduction of discrete SU(N) quantum spins. Spin ladders consisting of n transversely coupled spin chains lead to a CP(N-1) model with a vacuum angle theta=npi. In D-theory no sign problem arises and an efficient cluster algorithm is used to investigate theta-vacuum effects. At theta=pi there is a first order phase transition with spontaneous breaking of charge conjugation symmetry for CP(N-1) models with N>2. 相似文献
85.
Resonant Raman scattering experiments on n-Ge/n-GaAs (100) heterostructures reveal transitions involving quasi-two-dimensional electron states in Ge-accumulation layers. The experiments were performed in the range of the E1-gap of Ge. The electronic scattering transforms into E1-luminescence as the laser energy is tuned above the resonance. Spectra obtained at higher excitation energies show luminescence bands associated with the E1 and E1 + Δ1-gap of Ge. The latter results are compared with recent data for bulk heavily-doped Ge. 相似文献
86.
The variable-phase method is extended to calculate two-atom off-the-energy shell t-matrix elements. A study is presented of the off-shell wavefunctions and t-matrix elements of the HH pair, for both the lowest 1Σ and 3Σ interaction potentials. 相似文献
87.
A.S. Clough C.I. Beard D.V. Bugg J.A. Edgington J. Hall K. Bos J.C. Kluyver R.A. Kunne L. Linssen R. Birsa F. Bradamante S. Dalla Torre-Colautti M. Giorgi A. Martin A. Penzo P. Schiavon A. Villari S. Degli-Agosti D. Rapin 《Physics letters. [Part B]》1984,146(5):299-302
Measurements are reported of p?p total cross sections from 388 to 599 MeV/c in small momentum steps. Statistical errors are typically ±0.4%and the normalisation uncertainty is ±0.7%. There is no evidence for the “S-meson”. 相似文献
88.
Within the range of photon energies illuminating the Earth's surface, absorption of a photon by a conventional photovoltaic semiconductor device results in the production of a single electron‐hole pair; energy of a photon in excess of the semiconductor's bandgap is efficiently converted to heat through interactions between the electron and hole with the crystal lattice. Recently, colloidal semiconductor nanocrystals and nanocrystal films have been shown to exhibit efficient multiple electron‐hole pair generation from a single photon with energy greater than twice the effective band gap. This multiple carrier pair process, referred to as multiple exciton generation (MEG), represents one route to reducing the thermal loss in semiconductor solar cells and may lead to the development of low cost, high efficiency solar energy devices. We review the current experimental and theoretical understanding of MEG, and provide views to the near‐term future for both fundamental research and the development of working devices which exploit MEG. 相似文献