Analysis of the intermediate-band absorption properties of type-II GaSb/GaAs quantum-dot photovoltaics

Ramiro Gonzalez, Iñigo and Villa, Juan and Tablero Crespo, César and Antolín Fernández, Elisa and Luque López, Antonio and Martí Vega, Antonio and Hwang, J. and Phillips, J. and Martin, A.J. and Millunchick, J. (2017). Analysis of the intermediate-band absorption properties of type-II GaSb/GaAs quantum-dot photovoltaics. "Physical Review B", v. 96 ; pp. 125422-1. ISSN 1098-0121. https://doi.org/10.1103/PhysRevB.96.125422.

Description

Title: Analysis of the intermediate-band absorption properties of type-II GaSb/GaAs quantum-dot photovoltaics
Author/s:
  • Ramiro Gonzalez, Iñigo
  • Villa, Juan
  • Tablero Crespo, César
  • Antolín Fernández, Elisa
  • Luque López, Antonio
  • Martí Vega, Antonio
  • Hwang, J.
  • Phillips, J.
  • Martin, A.J.
  • Millunchick, J.
Item Type: Article
Título de Revista/Publicación: Physical Review B
Date: September 2017
ISSN: 1098-0121
Volume: 96
Subjects:
Faculty: Instituto de Energía Solar (IES) (UPM)
Department: Otro
UPM's Research Group: Silicio y Nuevos Conceptos para Células Solares
Creative Commons Licenses: None

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Abstract

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. ©2017 American Physical Society

Funding Projects

TypeCodeAcronymLeaderTitle
Madrid Regional GovernmentS2013/MAE-2780Madrid PVAntonio Martí VegaUnspecified

More information

Item ID: 47792
DC Identifier: http://oa.upm.es/47792/
OAI Identifier: oai:oa.upm.es:47792
DOI: 10.1103/PhysRevB.96.125422
Official URL: https://doi.org/10.1103/PhysRevB.96.125422
Deposited by: Prof. Antonio Martí Vega
Deposited on: 18 Sep 2017 07:52
Last Modified: 01 Oct 2018 22:30
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