Comparative study of optoelectronic properties of various Europium complexes used in organic electroluminescent structures.

International audienc

Imaging the Carrier Photogeneration in Nanoscale Phase Segregated Organic Heterojunctions by Kelvin Probe Force Microscopy

International audienc

Solution versus solid-state electropolymerization of regioregular conjugated fluorenone-thienylene vinylene macromonomers - voltammetric and spectroelectrochemical investigations

International audienc

Random and Regioregular Thiophene-Based Copolymers Containing Oligoaniline Side Chains: Synthesis, Spectroscopic and Spectroelectrochemical Investigations

International audienc

Organic red light emitting devices with europium complex in various multilayer structures.

International audienc

Unusually stable and highly electrochemically reversible n-doping of regioregular alternate copolymer of dialkylthiophene and fluorenone

We describe detailed studies on the electrochemical activity of thin films of a new conjugated copolymer, namely, poly[(2,7-fluoren-9-one)-alt-(5,5′-(3,3′-di-n-octyl-2,2′-bithiophene))] (abbreviated PFDOBT-HH (HH = head-to-head)), which has been synthesized electrochemically by a mild oxidation process at low current density. The dynamics of both p- and n-dopings of PFDOBT-HH in sulfolane/TEABF4 solution was fully characterized by a combination of cyclic voltammetry (CV) and electrochemical impedance spectroscopic (EIS) investigations. The development of a stable and highly electrochemically reversible n-doping capacity of the polymer film is presented as a function of the vertex potential in the CV curves of the n-doped PFDOBT-HH. Using EIS, clear evidence is furnished for the presence of trapped, negatively charged species in the polymer bulk as a consequence of prolonged, consecutive n-doping. Qualitative differentiation between the responses originating from mobile and trapped charge carriers has been established. In contrast to the cases of pristine polythiophene, polyfluorothiophene and nanoscale aryleneethynylene oligomers, n-doping of PFDOBT-HH, although leading to a partial trapping of the negatively charged carriers, does not result in any irreversible change in the electrochemical behavior of this polymer. Keywords: CV, PITT, n-doping, Charge trapping, Poly(fluorenone-bithiophene) copolyme

Composites of Double-Walled Carbon Nanotubes with bis-Quaterthiophene-Fluorenone Conjugated Oligomer: Spectroelectrochemical and Photovoltaic Properties.

International audienceA new composite consisting of a semiconducting oligomer, namely 2,7-bis-(3,3′′′-didodecyl-[2,2′,5′,2′′;5′′,2′′′]quaterthiophen-5-yl)-fluoren-9-one (QTF12), and double wall carbon nanotubes (DWCNT) has been prepared in view of its application as an active component in bulk heterojunction photovoltaic cells. Raman spectroelectrochemical investigations show that the onset of the oxidative doping of QTF12 in the presence of DWCNT occurs at E ) 0.475 V vs Ag/Ag+, that is, by 50 mV lower than in the case of pure QTF12. This effect was independently confirmed by UV-vis-NIR spectroelectrochemistry. The lowering of the oxidative doping potential, detected by spectroelectrochemistry, can be taken as a spectroscopic evidence of oligomer-nanotube interactions which result in raising, by 0.05 eV, the HOMO level of these QTF12 molecules which are at the interface with DWCNT. Bulk heterojunction test photovoltaic cells consisting of a ternary system (QTF12-DWCNT, PCBM) show the open circuit voltage (Voc) ) 0.53 V and the power conversion efficiency of 0.43%

Push–pull organic dyes and dye-catalyst assembly featuring a benzothiadiazole unit for photoelectrochemical hydrogen production

International audienceIn this work, we report the design and the preparation of two new dyes and a molecular dyad for the photoelectrochemical hydrogen production from water in a dye-sensitized photoelectrochemical cell (DSPEC). We designed dyes that include a benzothiadiazole (BTD) and an indacenodithiophene (IDT) units, and we obtained a new molecular dyad by covalent coupling with the cobalt diimine–dioxime catalyst. The introduction of the benzothiadiazole core in the structure improves the absorption properties and leads to an extension of the spectrum in the visible range up to 650 nm. The photoelectrochemical properties of the new dyad were evaluated on pristine and lithium-doped NiO electrodes. We demonstrate that increasing the light harvesting efficiency of the dyad by introducing a IDT–BTD chromophore is clearly beneficial for the photoelectrochemical activity. We also demonstrate that lithium doping of NiO, which improves the electronic conductivity of the mesoporous film, leads to a significant increase in performance, in terms of TON and F.E., more than doubled with our new dyad. This BTD-based molecular system outperforms the results of previously reported dyads using the same catalys

Synthesis, optoelectronic properties and photovoltaic performances of wide band-gap copolymers based on dibenzosilole and quinoxaline units, rivals to P3HT

International audienc