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Bel Haj Mohamed N.,Laboratoire des Interfaces et des Materiaux Avances LIMA | Bel Haj Mohamed N.,University of Monastir | Haouari M.,Laboratoire des Interfaces et des Materiaux Avances LIMA | Haouari M.,University of Monastir | And 12 more authors.
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2015

The role of organic capping ligand of semiconductor nanoparticles in dictating the interfacial charge transfer processes in hybrid semiconductor nanoparticles/polymer-based photovoltaic devices is investigated. Morphology, optical and structural study of the CdS nanoparticles and the hybrid material were accomplished using X-ray diffraction (XRD), absorption (UV-vis), atomic force microscopy (AFM), transmission electron microscopy (TEM), photoluminescence (PL) and time resolved photoluminescence spectroscopy (PLRT). A broad band absorption in UV-visible region and considerable fluorescence quenching of MEH-PPV in the composites are noted indicating a photo-induced charge transfer and dissociation of excitons. Time-resolved photoluminescence measurements indicating decreased lifetime further confirm this process. The solar cells open-circuit voltage and short-circuit current were improved using thiophenol modified CdS nanoparticles as electron acceptor in comparison to MEH-PPV only device demonstrating a promising approach to enhance charge transport in the hybrid nanoparticles-polymer composite photovoltaic cells (PV). © 2015 Elsevier B.V. All rights reserved.

Bouzidi M.,Unite de recherche sur les Hetero Epitaxies et Applications URHEA | Bouzidi M.,University of Monastir | Soltani S.,Unite de recherche sur les Hetero Epitaxies et Applications URHEA | Soltani S.,University of Monastir | And 6 more authors.
Solid State Sciences | Year: 2015

In this paper, we report a systematic investigation of the near band edge (NBE) excitonic states in GaN using low temperature photoluminescence (PL) and photoreflectance (PR) measurements. For this purpose, GaN films of different thicknesses have been grown on silicon nitride (SiN) treated c-plane sapphire substrates by atmospheric pressure metalorganic vapor phase epitaxy (MOVPE). Low temperature PR spectra exhibit well-defined spectral features related to the A, B and C free excitons denoted by FXA FXB and FXC, respectively. In contrast, PL spectra are essentially dominated by the A free and donor bound excitons. By combining PR spectra and Hall measurements a strong correlation between residual electron concentration and exciton linewidths is observed. From the temperature dependence of the excitonic linewidths, the exciton-acoustic phonon coupling constant is determined for FXA, FXB and FXC. We show that this coupling constant is strongly related to the exciton kinetic energy and to the strain level. © 2016 Elsevier Masson SAS.

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