Yvette Olivier

Bio: Yvette Olivier is an academic researcher from Université libre de Bruxelles. The author has contributed to research in topics: Electron mobility & Phase transition. The author has an hindex of 1, co-authored 1 publications receiving 81 citations.

Theoretical Characterization of the Structural and Hole Transport Dynamics in Liquid-Crystalline Phthalocyanine Stacks

Abstract: We present a joint molecular dynamics (MD)/kinetic Monte Carlo (KMC) study aimed at the atomistic description of charge transport in stacks of liquid-crystalline tetraalkoxy-substituted, metal-free phthalocyanines. The molecular dynamics simulations reproduce the major structural features of the mesophases, in particular, a phase transition around 340 K between the rectangular and hexagonal phases. Charge transport simulations based on a Monte Carlo algorithm show an increase by 2 orders of magnitude in the hole mobility when accounting for the rotational and translational dynamics. The results point to the formation of dynamical structural defects along the columns.

Ordered materials for organic electronics and photonics.

Abstract: We present a critical review of semiconducting/light emitting, liquid crystalline materials and their use in electronic and photonic devices such as transistors, photovoltaics, OLEDs and lasers. We report that annealing from the mesophase improves the order and packing of organic semiconductors to produce state-of-the-art transistors. We discuss theoretical models which predict how charge transport and light emission is affected by the liquid crystalline phase. Organic photovoltaics and OLEDs require optimization of both charge transport and optical properties and we identify the various trade-offs involved for ordered materials. We report the crosslinking of reactive mesogens to give pixellated full-colour OLEDs and distributed bi-layer photovoltaics. We show how the molecular organization inherent to the mesophase can control the polarization of light-emitting devices and the gain in organic, thin-film lasers and can also provide distributed feedback in chiral nematic mirrorless lasers. We update progress on the surface alignment of liquid crystalline semiconductors to obtain monodomain devices without defects or devices with spatially varying properties. Finally the significance of all of these developments is assessed.

Discotic Liquid Crystals for Opto-Electronic Applications †,‡

Abstract: Discotic liquid crystals (DLCs) have been exploited in opto-electronic devices for their advantageous properties including long-range self-assembling, self-healing, ease of processing, solubility in a variety of organic solvents, and high charge-carrier mobilities along the stacking axis. An overview of DLCs and their charge-carrier mobilities, theoretical modeling, alignment, and device applications is addressed herein. The effects of alignment on charge-carrier properties of DLCs are discussed. Particular attention is devoted to processing techniques that achieve suitable alignment of DLCs for efficient electronic devices such as zone-casting, zone melting, Langmuir−Blodgett deposition, solution-casting on preoriented polytetrafluoroethylene (PTFE), surface treatment, IR irradiation, application of a magnetic field, use of sacrificial layers, use of blends, application of an electric field, and others.

Microscopic Simulations of Charge Transport in Disordered Organic Semiconductors.

Abstract: Charge carrier dynamics in an organic semiconductor can often be described in terms of charge hopping between localized states. The hopping rates depend on electronic coupling elements, reorganization energies, and driving forces, which vary as a function of position and orientation of the molecules. The exact evaluation of these contributions in a molecular assembly is computationally prohibitive. Various, often semiempirical, approximations are employed instead. In this work, we review some of these approaches and introduce a software toolkit which implements them. The purpose of the toolkit is to simplify the workflow for charge transport simulations, provide a uniform error control for the methods and a flexible platform for their development, and eventually allow in silico prescreening of organic semiconductors for specific applications. All implemented methods are illustrated by studying charge transport in amorphous films of tris-(8-hydroxyquinoline)aluminum, a common organic semiconductor.

Absolute Rate of Charge Separation and Recombination in a Molecular Model of the P3HT/PCBM Interface

Abstract: A simplified model system is used to compute the rates of interfacial charge separation (CS) and recombination (CS) in the P3HT/PCBM blend (poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester) used in bulk heterojunction solar cells. The absolute charge-transfer rates of CS (kCS) and CR (kCR) processes were calculated to be 1.50 × 1011 and 1.93 × 109 s−1, respectively, from the Marcus−Levich−Jortner rate equation, in reasonable agreement with the range of available experimental values for a model containing a six thiophene rings chain and a single PCBM molecule. A detailed discussion of the inaccuracy intrinsic in the evaluation of all quantities entering the rate expression (equilibrium energy, electronic coupling, and internal and external reorganization energies) is provided together with a discussion of the sensitivity of the computed rate to these quantities. A variety of DFT methods is used to evaluate the states energy of the system (TDDFT, calculation with background charges, and...