Photoluminescence studies in CuInS2 thin films grown by sulfurization using ditertiarybutylsulfide

Abstract

The defect-related levels of CuInS2 thin films prepared by sulfurization using ditertiarybutylsulfide [(t-C4H9)2S:DTBS] have been investigated by photoluminescence (PL) spectroscopy. The PL spectra exhibit four peaks at 1.43, 1.27, 1.21, and 1.17 eV. On the basis of the PL spectra observed at various excitation intensities and temperatures, the peak emissions are attributed to donor–acceptor pair transitions. The ionization energies of donors in CuInS2 thin films are determined to be 66, 330, 300, and 150 meV, and the ionization energies of acceptors are estimated to be 100, 170, and 390 meV, respectively. As a result of the different sulfurization conditions and times, the donors corresponding to these ionization energies are due to indium interstitial (Ini), indium atoms-occupied sulfur vacancies (InS), sulfur atoms-occupied copper vacancies (SCu), and sulfur vacancies (VS), and the acceptors are determined to be due to copper vacancies (VCu), sulfur interstitial (Si), and sulfur atoms-occupied indium vacancies (SIn), respectively. Using these data, a band diagram for the defect levels of CuInS2 thin films has been proposed.

Sub-Bandgap Emission and Intraband Defect-Related Excited-State Dynamics in Colloidal CuInS2/ZnS Quantum Dots Revealed by Femtosecond Pump–Dump–Probe Spectroscopy

“…Steady-state spectroscopy performed on CIS QDs indicates the involvement of intragap states in the PL process, consistent with studies on CIS in thin film and bulk. [29][30][31][32]47 In this study, TA spectroscopy was performed on CIS/ZnS QDs, revealing two time constants (27 and 1.8 ps) in the recovery of the negative component. We identify the 27 ps time constant as Auger recombination and the 1.8 ps time constant as population flow into a surface defect state.…”

Effects of the CuS phase on the growth and properties of CuInS2 thin films

“…[18][19][20] On the other hand, the defect level of the sulfur atom-occupied copper vacancies (S Cu ) is a donor level, which is located at 280-300 meV below the conduction band. 8,19) The shallower level of the P1 peak at 160 ± 10 meV is determined to be due to the S i defect level, and the deeper level at 290 ± 10 meV is attributed to the S Cu defect level. In addition, the 1.21 eV emission peak has already been reported in our previous studies, 8,15) in which the transition from the S i level to the S Cu level is described.…”

“…8,19) The shallower level of the P1 peak at 160 ± 10 meV is determined to be due to the S i defect level, and the deeper level at 290 ± 10 meV is attributed to the S Cu defect level. In addition, the 1.21 eV emission peak has already been reported in our previous studies, 8,15) in which the transition from the S i level to the S Cu level is described. Therefore, the P1 peak emission is due to the transition from the S i level to the S Cu level.…”

“…4(a). 8,15) The temperature dependence of the integrated intensity I of the emission peak in the PL spectra of the thin films is most often described by the following expression: 16) XRD…”

“…The details of the equipment and process are described in our previous reports. [8][9][10] Sample #1 was sulfurized for 15 min at 515 °C and a DTBS flow rate of 35 µmol=min; this process is referred to as "single sulfurization". Sample #2 was successively sulfurized for 15 min at 515 °C and a DTBS flow rate of 35 µmol=min after the completion of single sulfurization; this process is referred to as "double sulfurization".…”