Photoluminescence Study of Defect Levels in CuInS₂ Thin Films Grown by Sulfurization Using Ditertiarybutylsulfide

Abstract

The defect-related photoluminescence (PL) levels of CuInS 2 thin films prepared by sulfurization using ditertiarybutylsulfide [(t-C 4 H 9 ) 2 S: 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.

Photoluminescence Study of Deep Levels in CuInS2 Thin Films Grown by Sulfurization Using Ditertiarybutylsulfide

“…The equipment used was the same as that described in our previous reports. [23][24][25] The thickness of the resulting Cu-rich, CuInS 2 thin films was measured to be approximately 2.0 m. X-ray diffraction (XRD) analysis revealed that the films were composed of a single phase with chalcopyrite structure, and no additional phases.…”

“…The PL peak P1 is due to DAP emission because the peak shifts to a higher energy as the excitation intensity increases. 24,25) In order to further identify the type of the peak P1 emission, excitation intensity dependence of the emission intensity in low temperature (77 K) is shown in Fig. 2(b).…”

“…The PL peak P2 is attributed to DAP emission because the peak energy exhibits a blue shift as the excitation intensity increases. 24,25) The excitation intensity as a function of the peak P2 emission intensity in low temperature (77 K) is shown in Fig. 4(b).…”

“…Ditertiarybutylsulfide [(t-C 4 H 9 ) 2 S: DTBS] is a less hazardous, very cheap and liquid metal-organic sulfide at room temperature, and is stored under atmospheric pressure in stainless-steel bubbles. Therefore, the risk of a widespread leakage is less likely than that of the case of H 2 S. In our previous study, [23][24][25] single-phase CuInS 2 thin films with chalcopyrite structure were prepared by sulfurization using DTBS. In addition, PL measurements were also conducted at low temperature in order to investigate the physical properties of defects in In-rich CuInS 2 thin films.…”

“…In addition, PL measurements were also conducted at low temperature in order to investigate the physical properties of defects in In-rich CuInS 2 thin films. 24) Temperature dependent and excitation intensity dependent PL measurements were also performed in CuInS 2 thin films. 25) In this paper, PL measurements were carried out on Curich CuInS 2 thin films grown by sulfurization using DTBS.…”