Deep and edge photoluminescence emission of CuInTe₂

Abstract

PACS 61.72. Ji, 71.55.Ht, 78.55.Hx Photoluminescence studies of chalcopyrite CuInTe 2 were conducted. Three edge (1.041 eV, 1.030 eV, and 1.019 eV) and two deep level (0.999 eV and 0.957 eV) emission bands were observed at 11 K. The excitation intensity dependence of PL spectra was recorded. As possible band sources one excitonic and four band-to-defect recombination mechanisms are proposed in this paper.CuInTe 2 (CIT) and other chalcopyrite ternary crystals have recently attracted worldwide interest because of their optimal bandgap (about 1 eV) for photovoltaic conversion devices. Also, they provide high conversion efficiencies at relatively low expense.Photoluminescence (PL) is an easy-to-use and sensitive probe of defect levels inside forbidden band. However, the most interesting and challenging part is the interpretation of the experimental spectra.In the present paper we discuss the photoluminescence spectrum of chalcopyrite CuInTe 2 . Previously, Rincón et al. have studied the photoluminescence of CIT crystals in Refs. [1,2]. In these papers edge and excitonic PL radiation was presented. In addition, we report also the radiative emission of deep recombination centres.The CuInTe 2 powder samples were synthesised from the elements at 810 °C in fused quartz ampoules. The treatment continued with homogenising annealing at 665 °C, which is slightly lower than the peritectic temperature in CuInTe 2 [3]. The starting Cu/In concentration ratio was 1.03. The final polycrystalline CuInTe 2 ingot showed a well-defined chalcopyrite pattern in the XRD scan.The sample was cooled inside a closed-cycle He cryostat (T = 8-300 K) and excited with a 441 nm He-Cd laser with maximum output power 40 mW. The PL signal was recorded by using standard lock-in technique, computer-controlled SPM-2 grating monochromator (f = 40 cm) and InGaAs detector. The detected signal was corrected in conformity with grating efficiency and detector sensitivity spectra.The experimental PL spectrum of a CIT sample at 11 K is presented in Fig. 1. We distinguished five different PL bands -three near the band-edge bands (E 1 , E 2 , and E 3 ) and two deep bands (D 1 and D 2 ) with their phonon replicas. We found that the replicas appear according to the LO-phonon energy ħω LO = 23.2 meV. The corresponding peak positions and the possible band origins are presented in Table 1. The results were compared with theoretical calculations of defect levels in CIT [4], where the model of effective mass theory was applied.We identified that three types of recombination mechanisms governed our bands: excitonic, donor to valence band, and conduction band to acceptor emission. It is known that shallow levels, because of the

Visible photoluminescence from chain Tl4In3GaSe8semiconductor

“…As seen from the figures 4(a) and (b), both bands change their intensities and peak positions with temperature changes: the peak intensities decrease as the temperature is increased and the peak positions show several degrees of red shift with increasing temperature (about 5 and 1 nm for B-and A-bands, respectively). The observed behaviour of the peak energy positions for the A-and B-bands satisfies the temperature dependence expected for free-tobound recombination [15,16].…”

Bandgap Fluctuations, Hot Carriers, and Band‐to‐Acceptor Recombination in Cu2ZnSn(S,Se)4 Microcrystals

“…Moreover, the PL band at low temperature has an asymmetric shape with a steeper decline on the high‐energy (HE) side. It was shown previously in many articles [ 6,20–22 ] that the LE side of these asymmetric PL bands at low temperatures is more or less determined by the density of states function ρ ( E ) while the temperature‐dependent distribution function f ( E ) controls the shape of the HE side of the PL band. A Gaussian density of states function is typical for defect‐related emission (BI) and for BT emission usually exponential shape is detected.…”

Research in solar cell technologies at Tallinn University of Technology

“…In recent years we have studied excitonic emission in CuInS 2 , including also a very deep emission related to the isoelectronic defects [3,4]. The edge emission resulting from highly doped ternaries has been studied experimentally and theoretically in AgGaTe 2 [5], CuGaTe 2 [6], AgInTe 2 [7], CuInTe 2 [8], and in other ternaries. The ordered defect compounds (ODC) have also attracted considerable interest not only because of their potential role in high-efficiency photovoltaic devices, but also as regards the understanding of structural properties of chalcopyrite ternary compounds.…”

“…With only one acceptor (A) and one donor (D) defect we expect 4 different PL bands to be present. Two of them are at higher energy than the lowest bandgap energy (E g A) and are related to the acceptor resonance state within the highest valence band[8].…”

“…PL spectra of three different samples of CuGaTe 2 measured at 10 K. The positions of A and B band gaps are also given as vertical lines[8].…”