Carrier extraction dynamics from Ge/Si quantum wells in Si solar cells

Takeshi Tayagaki, Yusuke Hoshi, Kazufumi Ooi, Takanori Kiguchi, Noritaka Usami

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


To address the carrier extraction mechanism that determines the fundamental characteristics, such as current density, open circuit voltage, and fill factor in nanostructure-based solar cells, we performed photoluminescence (PL) decay measurements of the Ge/Si quantum wells (QWs) in crystalline-silicon (c-Si) solar cells. We found that the PL decay time of Ge/Si QWs depends on the temperature and the applied electric field; this dependence reflects the carrier separation characteristics of electron-hole pairs in Ge/Si QWs. Above ∼ 40 K, the electron-hole pairs are rapidly separated by the thermal excitation and the built-in electric field of c-Si solar cells. In contrast, at 20 K the PL decay time remains almost unchanged for an applied electric field of up to ± 1 V. These results indicate that the electrons confined in the type-II band offsets could be thermally excited and then extracted by an applied electric field.

Original languageEnglish
Pages (from-to)368-371
Number of pages4
JournalThin Solid Films
Publication statusPublished - 2014 Apr 30


  • Photoluminescence
  • Quantum well
  • Semiconductor nanostructures
  • Solar cell

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Materials Chemistry


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