Sylvie Dabos-Seignon

A nonvolatile memory element based on an organic field-effect transistor

Organic field-effect transistors were fabricated with pentacene as the active material and a ferroelectric copolymer poly(vinylidene fluoride–trifluoroethylene) as the gate insulator. As-prepared devices showed normal p-type transistor operation. The ON- and OFF-states could be written to the device by applying appropriate voltages to the gate with respect to short-circuited source and drain electrodes. The devices exhibited excellent memory retention properties.

Pentacene: PTCDI-C13H27 molecular blends efficiently harvest light for solar cell applications

Solar cells exhibiting efficient photon harvesting are built from molecular blends of pentacene: PTCDI-C13H27. Absorption of the composition spans the whole visible spectrum with an onset at 730 nm. External quantum efficiency approaches unity at the peak absorption of pentacene. A 2.0% power conversion efficiency is obtained under 80 mW cm-2 AM 1.5 illumination, with 8.6 mA cm-2 short-circuit current. The comparison with bilayer devices suggests directions of improvement in conversion efficiency such as controlled growth of the blend layers.

Improved performance of pentacene field-effect transistors using a polyimide gate dielectric layer

Organic field-effect transistors using pentacene have been fabricated employing polyimide gate dielectric layers. The root-mean square surface roughness of polyimide films is 9 A. Devices with thin polyimide films as gate achieved a mobility of 0.16 cm2 V−1 s−1, threshold voltage −6.4 V, on–off ratio ~ 104 and subthreshold slope 7.5 dec−1 with the gate voltage span between 0 and −30 V. The upper limit of interface trap density has been estimated to be 3.9 × 1012 cm−2 eV−1. The mobility is found to be gate bias dependent.

Phthalimide end-capped thienoisoindigo and diketopyrrolopyrrole as non-fullerene molecular acceptors for organic solar cells

Two acetylene-bridged molecules, built by grafting phthalimides on thienoisoindigo (TII) and diketopyrrolopyrrole (DPP) blocks, have been synthesized, characterized and evaluated as electron acceptor materials in air-processed inverted organic solar cells. Once blended with poly(3-hexylthiophene), power conversion efficiencies (PCEs) of ca. 0.4% and 3.3% were achieved for TII and DPP based devices, respectively. To the best of our knowledge these PCEs (i) rank amongst the highest reported so far for diketopyrrolopyrrole based acceptors and (ii) make this contribution the very first example of thienoisoindigo based materials used as non-fullerene electron acceptors.

Multistate polarization addressing using a single beam in an azo polymer film

Peculiar light–matter interactions can break the rule that a single beam polarization can address only two states in an optical memory device. Multistate storage of a single beam polarization is achieved using self-induced surface diffraction gratings in a photoactive polymer material. The grating orientation follows the incident light beam’s polarization direction. The permanent self-induced surface relief grating can be read out in real time using the same laser beam.

Enantiopure versus Racemic Naphthalimide End-Capped Helicenic Non-fullerene Electron Acceptors: Impact on Organic Photovoltaics Performance

Impact of the enantiopurity on organic photovoltaics (OPV) performance was investigated through the synthesis of racemic and enantiomerically pure naphthalimide end-capped helicenes and their application as non-fullerene molecular electron acceptors in OPV devices. A very strong increase of the device performance was observed by simply switching from the racemic to the enantiopure forms of these π-helical non-fullerene acceptors with power conversion efficiencies jumping from 0.4 to about 2.0 % in air-processed poly(3-hexylthiophene)-based devices, thus highlighting the key role of enantiopurity in the photovoltaic properties.

Incoherent light-induced self-organization of molecules

Although coherent light is usually required for the self-organization of regular spatial patterns from optical beams, we show that peculiar light-matter interaction can break this evidence. In the traditional method of recording laser-induced periodic surface structures, a light intensity distribution is produced at the surface of a polymer film by an interference between two coherent optical beams. We report on the self-organization followed by propagation of a surface relief pattern. It is induced in a polymer film by using a low-power and small-size coherent beam assisted by a high-power and large-size incoherent and unpolarized beam. We demonstrate that we can obtain large size and well-organized patterns starting from a dissipative interaction. Our experiments open new directions to improving optical processing systems.

Multistate polarization addressing using one single beam in an azo polymer film: erratum

Peculiar light-matter interactions can break the rule that a single beam polarization can address only two states in an optical memory device. Multistate storage of a single beam polarization is achieved using self-induced surface diffraction gratings in a photo-active polymer material. The grating orientation follows the incident light beam polarization direction. The permanent self-induced surface relief grating can be readout in real time using the same laser beam.

Self-Induced Diffraction Grating Storage in Polymer Films

ABSTRACT Peculiar light-matter interactions can break the rule that a single beam polarization can address only two states in an optical memory device. Multistate storage of a single beam polarization is achieved using self-induced surface diffraction gratings in a photo-active polymer material. The grating orientation follows the incident light beam polarization direction. The permanent self-induced surface relief grating can be readout in real time using the same laser beam.

Neuron growth engineering on a photoinduced surface relief grating: a tool for plastic neuroelectronics

The orientation and attachment of neuronal cells were controlled by submicron-scale topographical patterns. The surface structure is realized with a laser beam and photo-responsive azobenzene polymer thin films. A surface relief grating (SRG) can be produced by self-organization of molecules under the action of light. The cells are attached onto the SRG and preferentially grown along the groove direction. The use of polymer thin films is good candidate for cellular engineering applications.