Photoluminescence study of polycrystalline photovoltaic CdS thin film layers grown by close-spaced sublimation and chemical bath deposition

Abstract

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Photoluminescence ͑PL͒ measurements were used to study the effect of postdeposition treatments by annealing and CdCl 2 activation on polycrystalline CdS layer grown by close-spaced sublimation ͑CSS͒ and chemical bath deposition ͑CBD͒. CdS films were either annealed in a temperature range of 200-600°C or CdCl 2 treated between 300-550°C. The development of "red," "intermediate orange," "yellow," and "green" luminescence bands is discussed in comparison with PL assignments found in literature. PL spectra from CdS layer grown by CSS are dominated by the yellow band with transitions at 2.08 and 1.96 eV involving ͑Cd i -A͒, ͑V S -A͒ complex states where A represents an acceptor. Green luminescence bands are observed at 2.429 and 2.393 eV at higher annealing temperature of 500-600°C or CdCl 2 treatment above 450°C, and these peaks are associated with zero and a longitudinal optical phonon replica of "free-to-bound" transitions. As grown CBD-CdS films show a prominent red band with four main peaks located at 1.43, 1.54, 1.65, and 1.77 eV, believed to be phonon replicas coupled with local vibrational modes. This remains following postdeposition treatment. The red luminescence is associated with V S surface states and in the case of CdCl 2 treatment with ͑V Cd -Cl S ͒ centers. Postdeposition treatments of CBD and CdS promote the evolution of an intermediate orange band at 2.00 eV, most likely a donor-acceptor pair, and a yellow band at 2.12 eV correlated with ͑Cd i -V Cd ͒ centers. The green luminescence bands observed at 2.25 and 2.34 eV are associated with transitions from deep donor states ͑e.g., Cd i ͒ to the valence band. These states form due to crystallinity enhancement and lattice conversion during annealing or CdCl 2 activation. Observed changes in PL bands provide detailed information about changes in radiative recombination centers in CdS layer, which are suggested to occur during device processing of CdTe/CdS thin film solar cells.

Cu-doped CdS and its application in CdTe thin film solar cell

“…The broad defect-related band located around 1.5-2.0 eV is ascribed to the emission between the energy levels of the defects, such as, Cd vacancy (V Cd ), surface states, Cl at the lattice of S (Cl S ), S vacancy (V S ), interstitial Cd (Cdi) and the the valence band state (VB), impurities and acceptor. [24][25][26] The detailed peak components, which are ascribed to the specific emissions, are shown in Fig. 4(b).…”

Rare earths (Ce, Eu) molar concentration-dependent of the structural and optical properties of CBD-CdS nanofilms

“…For four studied CBD-CdS samples, another broad band, band d, is observed around 1.88 eV, this band named the "orange band" has been observed between 2.03-2.08 eV [40,41], it is possibly associated to a donoracceptor pair (DAP) radiative transition between a donor level related to interstitial cadmium (I 2+ Cd ) and an unidentified acceptor level. The ionization energy of this donor has estimated to be between 0.12 and 0.26 eV, which corresponds to (I 2+ Cd ) [38].…”

Temperature-dependent photoluminescence and mechanism of CdS thin film grown on Si nanoporous pillar array

“…Accordingly a lot of preparing techniques, such as spray pyrolysis [8], close-spaced sublimation [9], chemical vapor deposition [10] and chemical bath deposition (CBD) [9] etc., have been developed for growing high-quality CdS thin films on different substrates. Among the methods, CBD deposition is thought to be most suitable for preparing CdS thin films with large-area uniformity, strong film-substrate adhesion and high reproducibility.…”