The defect-related photoluminescence (PL) levels of CuInS 2 thin films prepared by sulfurization using ditertiarybutylsulfide [(t-C 4H 9) 2S: DTBS] have been investigated. The PL spectra exhibit three low-energy peaks at 1.37, 1.34, and 1.24 eV. On the basis of these PL spectra observed at different excitation intensities, the emissions are attributed to donor-acceptor pair transitions. The ionization energies of donors in CuInS 2 thin films are determined to be 125, 150, and 280 meV, which are, respectively, due to indium atom-occupied copper vacancies (In Cu), sulfur vacancies (V S), and sulfur atom-occupied copper vacancies (S Cu); whereas that of the acceptor is determined to be 100 meV and has been reported to the copper vacancy (V Cu). Using these data, a band diagram for the defect levels of CuInS 2 thin films prepared by sulfurization is proposed.
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