Browsing by Author "Saldias, Cesar"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Biocomposites with increased dielectric constant based on chitosan and nitrile-modified cellulose nanocrystals
    (2018) Bonardd Salvador, Sebastián Ignacio; Robles, Eduardo; Barandiaran, Irati; Saldias, Cesar; Leiva Campusano, Ángel; Kortaberria, Galder
  • Thumbnail Image
    Item
    Evaluation of electro-synthesized oligothiophenes as donor materials in vacuum-processed organic photovoltaic devices
    (2023) Camarada, Maria Belen; Saldias, Cesar; Castro-Castillo, Carmen; Angel, Felipe A.
    2,2 ':5 ',2 ''-terthiophene (3Th) was utilized as a precursor in the electro-synthesis of oligothiophenes and their further evaluation as donor materials in the active layer of vacuum-processed organic photovoltaic (OPV) devices. Electro-polymerization conditions were optimized to obtain a controlled fraction of polydisperse oligomers, as demonstrated by size exclusion chromatography (SEC). The polydispersity of the material was further decreased during thermal evaporation, where a reduced fraction of the oligomer was deposited, as observed by SEC, absorption spectroscopy, and the characterization of the fabricated devices. Our results demonstrate for the first time the potential of the electro-synthesis of oligothiophenes as active materials for their application in bulk heterojunction for OPV devices.
  • Thumbnail Image
    Item
    New Benzotriazole and Benzodithiophene-Based Conjugated Terpolymer Bearing a Fluorescein Derivative as Side-Group: In-Ternal Forster Resonance Energy Transfer to Improve Organic Solar Cells
    (MDPI, 2022) Jessop, Ignacio A.; Cutipa, Josefa; Perez, Yasmin; Saldias, Cesar; Fuentealba, Denis; Tundidor-Camba, Alain; Terraza, Claudio A.; Camarada, Maria B.; Angel, Felipe A.
    A new benzodithiophene and benzotriazole-based terpolymer bearing a fluorescein derivative as a side group was synthesized and studied for organic solar cell (OSC) applications. This side group was covalently bounded to the backbone through an n-hexyl chain to induce the intramolecular Forster Resonance Energy Transfer (FRET) process and thus improve the photovoltaic performance of the polymeric material. The polymer exhibited good solubility in common organic chlorinated solvents as well as thermal stability (TDT10% > 360 degrees C). Photophysical measurements demonstrated the occurrence of the FRET phenomenon between the lateral group and the terpolymer. The terpolymer exhibited an absorption band centered at 501 nm, an optical bandgap of 2.02 eV, and HOMO and LUMO energy levels of -5.30 eV and -3.28 eV, respectively. A preliminary study on terpolymer-based OSC devices showed a low power-conversion efficiency (PCE) but a higher performance than devices based on an analogous polymer without the fluorescein derivative. These results mean that the design presented here is a promising strategy to improve the performance of polymers used in OSCs.
  • Thumbnail Image
    Item
    Spontaneous Adsorption of Gold Nanoparticles by Polyelectrolyte Thin Films
    (AMER SCIENTIFIC PUBLISHERS, 2012) Urzua, Marcela; Leiva, Angel; Espinoza Beltran, Francisco J.; Briones, Ximena; Saldias, Cesar; Pino, Maximiliano
    Nanocomposed films constituted by gold nanoparticles immobilized onto polyelectrolytes were obtained and studied. To obtain the films, amino terminated silicon wafer surfaces were put in contact with aqueous solution of polyelectrolytes derived from Poly(maleic anhydride-alt-styrene) containing aryl and amine-alkyl groups in the side chains, in this condition the adsorption of macromolecules was achieved. The effects of the chemical nature of the side chains and ionic strength on the amounts of adsorbed polyelectrolytes were studied by ellipsometry. The adsorption of polyelectrolytes increases with increasing ionic strength in agreement with the screening-enhanced adsorption regime; the results are discussed considering the steric hindrance of the side chains and flexibility of the polymers. A spontaneous adsorption process of nanoparticles onto polyelectrolyte films took place when these last were immersed in a gold nanoparticles suspension. The adsorption amounts were qualitatively evaluated by SEM and AFM and these showed to be dependent on chemical structure of polyelectrolytes.