Linear and nonlinear optical absorption characterization of natural laccaic acid dye

We report on the optical performances of laccaic acid dye in solution at different concentrations and dye–poly(methyl methacrylate) composite thin films. The linear spectral characteristics including optical constants, i.e. refractive index (n) and extinction coefficient (k), were carried out in a comprehensive way through absorbance, fluorescence and ellipsometric studies. The nonlinear optical parameters such as nonlinear absorption coefficient β eff (or β 2), the imaginary third-order susceptibility (Im[χ (3)]) and the imaginary part of second-order hyperpolarizability (γ) of the samples were evaluated using the open-aperture Z-scan technique with a laser pulse duration of 10 ns at 532 nm wavelength. The corresponding numerical values of these parameters were of 10−10, 10−11 and 10−32 order, respectively. Two-photon absorption was revealed to be the main driving physical mechanism in the nonlinear response. This suggests that laccaic acid dye can be a potential candidate for NLO materials application

P3HT:PCBM based solar cells: a short review focusing on ZnO nanoparticles buffer layer, post-fabrication annealing and an inverted geometry

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.Today, bulk heterojunction (BHJ) organic solar cells (OSCs) dominate modern age research in renewable solar energy. In recent developments, the ultimate goal is to improve the general performance of the BHJ-OSCs to enable them to compete on an equal footing basis with conventional silicon photovoltaic cells. In this presentation, we review the fundamental parameters that have been reported to improve the general performance of the BHJ-OSC devices. These parameters include, among other things, the use ZnO nanoparticles electron transport layer (ETL) inserted between the top electrode and the photoactive layer, annealing procedure and device geometry. The BHJ-OSC devices constructed in this study comprised of successive (bottom up) layers of (3,4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl butyric acid methyl ester (PCBM) layer, zinc oxide (ZnO) nanoparticles and aluminum (Al) metal top electrode. These layers were deposited on indium tin oxide (ITO) coated glass substrates. The device construction was also inverted (top down) in order to evaluate the effect of inversion on the power conversion efficiency and the general performance of the devices. The devices were annealed at 155 oC either before (pre-annealed) or after (post-annealed) the deposition of the Al top electrode. Post-annealed devices showed improved photovoltaic (PV) characteristics when compared to pre-annealed devices. Furthermore, we discuss the performance of inverted geometry in comparison to ZnO nanoparticles and nanoflakes as buffer layers.cf201

Effect of heat treatment on the migration behaviour of Sr and Ag CO-implanted in glassy carbon

The effect of annealing on the diffusion of silver, silver and strontium co-implanted in glassy carbon was investigated. Glassy carbon samples were implanted with 360 keV Ag ions at room temperature. The RBS profile showed that Fickian diffusion of Ag in glassy carbon is only observed at temperatures ranging from 500 °C–600 °C. At higher annealing temperatures, there was a significant loss of Ag and no Ag was retained in glassy carbon at 700 °C. Glassy carbon samples were also co-implanted with Ag and Sr. The diffusion behaviour of Ag when co-implanted with Sr was similar to that of the singly implanted Ag sample. However, the introduction of Sr into the glassy carbon matrix assisted in the retainment of the Ag ions. The co-implantation of Ag and Sr resulted in a change in the diffusion behaviour of Sr in glassy carbon. The implantation of Ag with Sr prevented the movement of Sr deeper into the bulk of the glassy carbon. The non-movement of Sr into the bulk of the glassy carbon was attributed to the increase of radiation damage near the surface of the glassy carbon making diffusion of Sr towards the surface of glassy carbon an easier choice.The National Research Foundation, South Africa and the TWAS-DFG Co-operation Programme.http://www.journals.elsevier.com/vacuumhj2021Physic

Changes in the mechanical, structural and electrical properties of glassy carbon due to strontium and silver co-implantation and annealing

Please read abstract in the article.https://www.elsevier.com/locate/apsusc2022-09-22hj2022Physic

Optical and structural properties of nanostructured ZnO thin films deposited onto FTO/glass substrate by a solution-based technique

Nanostructured zinc oxide thin films were spin coated on conductive glass substrates via a sol-gel based technique using zinc acetate dihydrate as precursor. The pH of the alkalis used as catalytic agents in the hydrolysis step is shown to have a strong effect on the structural and morphological properties of the deposited ZnO. The size of the particles was observed by Transmission Electron Microscopy (TEM), while Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) and Atomic Force Microscopy (AFM), were used to analyze the morphology of the films. X-ray iffraction (XRD) and Raman spectra provided evidence of crystal growth together with an increase in the crystalline degree of the hexagonal wurtzite structure after annealing. The bandgap energy was estimated by Tauc´s method and found to decrease after annealing, which is attributed to an increase in the crystallite size and to the presence of less defect sites. A good correlation between crystallite size and absorption edges was found. The photoluminescence spectra of as-deposited samples depend on the nature and pH values of catalytic agent used, and reveal the presence of a broad visible emission attributed to a variety of intrinsic defects.Fil: Berruet, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina;Fil: Pereyra, C.J.. Universidad de la República. Facultad de Ingenieria. Instituto de Física. Centro Interdisciplinario de Nanotecnología, Química y Física de Materiales; Uruguay;Fil: Mhlongo, G.H.. Council for Scientific and Industrial Research. National Centre for Nano-Structured Materials; Sudafrica;Fil: Dhlamini, M.S.. Council for Scientific and Industrial Research. National Centre for Nano-Structured Materials; Sudafrica; University of South Africa. Department of Physics; Sudafrica;Fil: Hillie, K.T.. Council for Scientific and Industrial Research. National Centre for Nano-Structured Materials; Sudafrica; University of the Free State. Department of Physics; Sudafrica;Fil: Vazquez, Marcela Vivian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina;Fil: Marotti, R.E.. Universidad de la Republica. Facultad de Ingenieria. Instituto de Fisica y CINQUIFIMA; Uruguay

Substrate temperature dependence of structure and optical properties of ZnTiO3:Er3+/Yb3+ thin films synthesized by pulsed laser deposition

ZnTiO3:Er3+,Yb3+ thin film phosphors were successfully deposited by pulsed laser deposition (PLD) at different substrate temperatures. The distribution of the ions in the films was investigated and the chemical analysis showed that the doping ions were homogeneously distributed in the thin films. The optical response of the phosphors revealed that the reflectance percentages of the ZnTiO3:Er3+,Yb3+ vary with the silicon substrate temperature due to the differences in the thickness and morphological roughness of the thin films. Under 980 nm diode laser excitation, the ZnTiO3:Er3+,Yb3+ film phosphors displayed up-conversion emission from the Er3+ electronic transitions, with violet, blue, green, and red emission lines at 410, 480, 525, 545 and 660 nm from 2H9/2 → 4I15/2, 4F7/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions, respectively. The up-conversion emission was enhanced by increasing the silico (Si) substrate temperature during the deposition. Based on the photoluminescence properties and decay lifetime analysis, the energy level diagram was established and the up-conversion energy-transfer mechanism was discussed in detail

Photoluminescence and phase related cathodoluminescence dynamics of Pr3+ doped in a double phase of ZnTa2O6 and ZnAl2O4

A new phosphor ZnTaAlO5:Pr3+, which displays cathodoluminescence intensity that is phase dependent, was synthesised by solid statereaction. x-ray diffraction, scanning electron microscopy and EDX (energy dispersive x-ray spectroscopy) maps were used to confirm the multi-phase, multi-particle shapes and to assign each particle shape o a corresponding phase of the phosphor, respectively. Cathodoluminescence mapswere obtained simultaneously with the EDX maps, and showed both the luminescence emerging from intrinsic and extrinsic defect centres. Theactivator red emission was better resolved using photoluminescence spectroscopy, which showed emission lines emerging from more than onemanifold of the Pr3+transitions. The persistent luminescence was measured and the corresponding electron trapping centres were characterisedby thermoluminescence spectroscopy.This work is based on financial contribution from the South African Research Chairs Initiative of the Department of Science and Technology (84415), National Research Foundation of South Africa and the Erasmus Mundus–Saturn action 2 programme funded by the European Union (2014/2015).A new phosphor ZnTaAlO5:Pr3+, which displays cathodoluminescence intensity that is phase dependent, was synthesised by solid statereaction. x-ray diffraction, scanning electron microscopy and EDX (energy dispersive x-ray spectroscopy) maps were used to confirm the multi-phase, multi-particle shapes and to assign each particle shape o a corresponding phase of the phosphor, respectively. Cathodoluminescence mapswere obtained simultaneously with the EDX maps, and showed both the luminescence emerging from intrinsic and extrinsic defect centres. Theactivator red emission was better resolved using photoluminescence spectroscopy, which showed emission lines emerging from more than onemanifold of the Pr3+transitions. The persistent luminescence was measured and the corresponding electron trapping centres were characterisedby thermoluminescence spectroscopy