Hammam-Lif, Tunisia
Hammam-Lif, Tunisia

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Zaghdoudi W.,Photovoltaic Laboratory Research | Dammak T.,University of Sfax | Chtourou R.,Photovoltaic Laboratory Research
Superlattices and Microstructures | Year: 2014

In this work, we present the confinement effect of the incorporation of perovskite compounds (C12H25-NH3) 2PbI4 quantum wells into different porous anodic aluminum oxide (PAA) matrix via a chemical route. The detailed structure and optical property of the quantum wells in PAA were characterized by FT-IR, UV-Vis absorption and photoluminescence (PL) spectroscopy. The surface topography for the two used PAA matrix has been studied using atomic force microscopy (AFM). The pores diameters (pores spacing) for the two matrix are 15 (35 nm) and 45 (82 nm). UV-visible and photoluminescence spectroscopy of (C12H 25-NH3)2PbI4/PAA exhibits a clear blue shift of the fundamental excitonic transition. This effect is attributed to the confinement of the exciton mode in the pore of the PAA matrix. © 2014 Elsevier Ltd. All rights reserved.

Ghrib M.,Photovoltaic Laboratory Research | Gaidi M.,Photovoltaic Laboratory Research | Khedher N.,Photovoltaic Laboratory Research | Ghrib T.,Photovoltaic Laboratory Research | And 2 more authors.
Applied Surface Science | Year: 2011

In this paper we report detail investigation and correlation between micro-structural and optical properties of nanocrystalline silicon (nc-Si) deposited by plasma enhancement chemical vapor deposition (PECVD) on porous aluminum structure. The influence of the microstructure of the nc-Si thin films on their optical properties was investigated through an extensive characterization. The effect of anodisation currents on the microstructure of aluminum surface layer and nc-Si films was systematically studied by atomic force microscopy (AFM) and transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD). The optical constants (n and k as a function of wavelength) of the films were obtained using variable angle spectroscopic ellipsometry (SE) in the UV-vis-NIR regions. The silicon layer (SL) was modeled as a mixture of void, crystalline silicon and aluminum using the Bruggeman approximation. Based on this full characterization, it is demonstrated that the optical characteristics of the films are directly correlated to their micro-structural properties. A very bright photoluminescence (PL) was obtained and find to depend on anodisation current. © 2010 Elsevier B.V.

Gaidi M.,INRS - Institute National de la Recherche Scientifique | Gaidi M.,Photovoltaic Laboratory Research | Hajjaji A.,INRS - Institute National de la Recherche Scientifique | Hajjaji A.,Photovoltaic Laboratory Research | And 3 more authors.
Journal of Applied Physics | Year: 2010

Tin oxide (SnO2) ultrathin films were deposited by pulsed laser deposition (PLD) onto SiO2 /Si and quartz substrates, at various nominal thicknesses ranging from isolated nanoparticles (NPs) to ∼300 nm -thick films, under an oxygen background pressure of 10 mTorr. The microstructural and surface morphologies of the NP-based SnO2 films were characterized by x-ray diffraction and atomic force microscopy, as a function of their nominal film thickness. The PLD- SnO2 films were found to be composed of NPs (in the 1-6 nm range), whose size increases with the film thickness. The energy band gap, as determined from the absorption edge, was found to shift to higher values with decreasing the film thickness (i.e., decreasing the NPs size). It was found that an annealing at 700 °C under O2 ambient is a prerequisite to get a photoluminescence (PL) emission from the PLD- SnO2 films. The PL of the annealed SnO2 films was found to consist of two broad emission bands, regardless of the SnO2 film thickness. The first band is composed of 3 PL subbands peaking at 3.20, 3.01, and 2.90 eV, while the second one is centered on 2.48 eV. In spite of the observed band-gap widening (as confirmed by theoretical calculation), we show that surface state (e.g., oxygen vacancies) dominate completely the PL emission of SnO2 NPs, which becomes more luminescent as the NPs size decreases while the PL energy remains unchanged. The PL properties of the PLD- SnO2 NPs are discussed in terms of defects and/or oxygen vacancies related transitions. © 2010 American Institute of Physics.

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