Na-Dependent Ultrafast Carrier Dynamics of CdS/Cu(In,Ga)Se2 Measured by Optical Pump-Terahertz Probe Spectroscopy

Woo Jung Lee, Dae Hyung Cho, Jae Hyung Wi, Won Seok Han, Yong Duck Chung, Jaehun Park, Jung Min Bae, Mann Ho Cho

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15 Citations (Scopus)


To investigate the origin of the Na effect on photovoltaic (PV) devices, Cu(In,Ga)Se2 (CIGS) and CdS/CIGS layers were grown on borosilicate (BS) and soda-lime glass (SLG), respectively. The defect states and nonequilibrium carrier dynamics of the samples were measured using photoluminescence (PL) and optical pump-THz probe (OPTP) spectroscopy. From the PL results, we discovered that different shallow donor-acceptor levels were formed in the CIGS layer grown on BS and SLG, respectively. In the OPTP results, relaxation times of photocarriers excited from the CdS/CIGS layer were clearly distinguishable, and are explained by the formation of different defect states depending on substrates. In BS, deep defect level 'DX states' were formed in the Eg near the p-n junction, which induce trapping photocarriers, resulting in shortening relaxation time. In SLG, there was no "DX state", which clearly demonstrates the positive effect of Na atoms at the p-n junction on performance of PV devices.

Original languageEnglish
Pages (from-to)20231-20236
Number of pages6
JournalJournal of Physical Chemistry C
Issue number35
Publication statusPublished - 2015 Jul 6

Bibliographical note

Publisher Copyright:
© 2015 American Chemical Society.

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films


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