Relaxation of localized excitons by phonon emission at oxygen vacancies in Cu2O

Sandhaya Koirala, Mitsuyoshi Takahata, Yuji Hazama, Nobuko Naka, Koichiro Tanaka

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We have studied the relaxation mechanism of localized excitons at optically active defect centers in cuprous oxide by the photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. We find that the temperature dependence of the PL and PLE spectra of the oxygen vacancy emission is well explained by the adiabatic potential model. The Huang-Rhys factors for the absorption and emission processes are obtained as ∼8, indicating the medium coupling of the exciton-phonon interaction. The effective frequencies of the vibrational levels are obtained as 16.5 meV and 16.1 meV, respectively, for the excited and ground states. These results indicate the Stokes shift of 0.269 ±0.008 eV which is released from the localized excitons as the lattice relaxation energy by phonon emission. Our energy level diagram resolves the previous discrepancy between the small activation energy and the large separation of the luminescence photon energies for free and localized excitons.

Original languageEnglish (US)
Pages (from-to)65-69
Number of pages5
JournalJournal of Luminescence
StatePublished - Nov 2014

Bibliographical note

Funding Information:
S.K. and Y.H. are grateful for the support by the Grant-in-Aid for the Global COE program “The Next Generation of Physics, Spun from Universality and Emergence” from MEXT, Japan. N.N. acknowledges support by the core-stage backup project of Kyoto University .


  • Adiabatic potential model
  • Defect center
  • Relaxed exciton


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