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Memorias de investigación
Artículos en revistas:
Analysis of the intermediate-band absorption properties of type-II GaSb/GaAs quantum-dot photovoltaics
Año:2017
Áreas de investigación
  • Energía solar,
  • Semiconductores,
  • Física,
  • Puntos cuanticos,
  • Células solares
Datos
Descripción
Quantum-dot (QD) intermediate-band (IB) materials are regarded as promising candidates for high-efficiency photovoltaics. The sequential two-step two-photon absorption processes that take place in these materials have been proposed to develop high-efficiency solar cells and infrared (IR) photodetectors. In this work, we experimentally and theoretically study the interrelation of the absorptivity with transitions of carriers to and from the IB in type-II GaSb/GaAs QD devices. Our devices exhibit three optical band gaps with: EL = 0.49 eV, EH = 1.02 eV, and EG = 1.52 eV, with the IB located 0.49 eV above the valence band. These values are well supported by semiempirical calculations of the QDs electronic structure. Through intensity-dependent two-photon photocurrent experiments, we are able to vary the filling state of the IB, thus modifying the absorptivity of the transitions to and from this band. By filling the IB with holes via E = 1.32 eV or E = 1.93 eV monochromatic illumination, we demonstrate an increase in the EL-related absorptivity of more than two orders of magnitude and a decrease in the EH-related absorptivity of one order of magnitude. The antisymmetrical evolution of those absorptivities is quantitatively explained by a photoinduced shift of the quasi-Fermi level of the IB. Furthermore, we report the observation of a two-photon photovoltage, i.e., the contribution of subband gap two-photon absorption to increase the open-circuit voltage of solar cells. We find that the generation of the two-photon photovoltage is related, in general, to the production of a two-photon photocurrent. However, while photons with energy close to EL participate in the production of the two-photon photocurrent, they are not effective in the production of a two-photon photovoltage.We also report the responsivity of GaSb/GaAs QD devices performing as optically triggered photodetectors. These devices exhibit an amplification factor of almost 400 in the IR spectral region. This high value is achieved by minimizing?via doping?the absorptivity in the IR range of the QDs under equilibrium conditions.
Internacional
Si
JCR del ISI
Si
Título de la revista
Physical Review B
ISSN
2469-9950
Factor de impacto JCR
3,836
Información de impacto
Volumen
96
DOI
10.1103/PhysRevB.96.125422
Número de revista
12
Desde la página
125422
Hasta la página
125435
Mes
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Participantes
  • Autor: Iñigo Ramiro Gonzalez (UPM)
  • Autor: Juan Villa Morales (UPM)
  • Autor: Cesar Tablero Crespo (UPM)
  • Autor: Elisa Antolin Fernandez (UPM)
  • Autor: Antonio Luque Lopez (UPM)
  • Autor: Antonio Marti Vega (UPM)
  • Autor: J. Hwang
  • Autor: J. Phillips
  • Autor: A. J. Martin
  • Autor: J. Millunchick
Grupos de investigación, Departamentos, Centros e Institutos de I+D+i relacionados
  • Creador: Centro o Instituto I+D+i: Instituto de Energía Solar
  • Departamento: Electrónica Física, Ingeniería Eléctrica y Física Aplicada
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