排序方式: 共有44条查询结果,搜索用时 156 毫秒
41.
42.
Wahnón P Conesa JC Palacios P Lucena R Aguilera I Seminovski Y Fresno F 《Physical chemistry chemical physics : PCCP》2011,13(45):20401-20407
Intermediate band materials can boost photovoltaic efficiency through an increase in photocurrent without photovoltage degradation thanks to the use of two sub-bandgap photons to achieve a full electronic transition from the valence band to the conduction band of a semiconductor structure. After having reported in previous works several transition metal-substituted semiconductors as able to achieve the electronic structure needed for this scheme, we propose at present carrying out this substitution in sulfides that have bandgaps of around 2.0 eV and containing octahedrally coordinated cations such as In or Sn. Specifically, the electronic structure of layered SnS(2) with Sn partially substituted by vanadium is examined here with first principles quantum methods and seen to give favourable characteristics in this respect. The synthesis of this material in nanocrystalline powder form is then undertaken and achieved using solvothermal chemical methods. The insertion of vanadium in SnS(2) is found to produce an absorption spectrum in the UV-Vis-NIR range that displays a new sub-bandgap feature in agreement with the quantum calculations. A photocatalytic reaction-based test verifies that this sub-bandgap absorption produces highly mobile electrons and holes in the material that may be used for the solar energy conversion, giving experimental support to the quantum calculations predictions. 相似文献
43.
Results of density-functional calculations for indium thiospinel semiconductors substituted at octahedral sites with isolated transition metals (M=Ti,V) show an isolated partially filled narrow band containing three t2g-type states per M atom inside the usual semiconductor band gap. Thanks to this electronic structure feature, these materials will allow the absorption of photons with energy below the band gap, in addition to the normal light absorption of a semiconductor. To our knowledge, we demonstrate for the first time the formation of an isolated intermediate electronic band structure through M substitution at octahedral sites in a semiconductor, leading to an enhancement of the absorption coefficient in both infrared and visible ranges of the solar spectrum. This electronic structure feature could be applied for developing a new third-generation photovoltaic cell. 相似文献
44.
Miguel?A.?Mu?oz-Márquez Estefanía?Guerrero Asunción?Fernández Patricia?Crespo Antonio?Hernando Raquel?Lucena José?C.?Conesa 《Journal of nanoparticle research》2010,12(4):1307-1318
Magnetometry results have shown that gold NPs (∼2 nm in size) protected with phosphine and chlorine ligands exhibit permanent
magnetism. When the NPs size decreases down to the subnanometric size range, e.g. undecagold atom clusters, the permanent
magnetism disappears. The near edge structure of the X-ray absorption spectroscopy data points out that charge transfer between
gold and the capping system occurs in both cases. These results strongly suggest that nearly metallic Au bonds are also required
for the induction of a magnetic response. Electron paramagnetic resonance observations indicate that the contribution to magnetism
from eventual iron impurities can be disregarded. 相似文献