AMADEus Seminar - Towards the microscopic modeling of organic light-emitting devices - Wednesday 19 November 2014, 04:30 pm - ICMCBle 19 novembre 2014 à 16h30
Part I: Thermally Activated Delayed Fluorescence in organic emitters: a molecular picture
Juan-Carlos Sancho-García (email@example.com)
Departamento de Química Física
Universidad de Alicante, Spain
Abstract: New materials for OLED applications with low singlet-triplet energy splitting have been recently synthesized in order to allow for the e?cient conversion of triplet into singlet excitons (emitting light) via a Thermally Activated Delayed Fluorescence (TADF) process. Accurately predicting this singlet-triplet energy splitting is key to the understanding and further design of organic materials, but the prediction which may be hampered by the charge-transfer nature of the states involved [1,2]. The accurate modeling of these states with Time-Dependent Density Functional Theory (TD-DFT) is thus highly challenging, and possible insights might be masked by routine drawbacks of the calculations . We will thus address this issue by carefully examining how to systematically reduce as much as possible the underlying error bar of any calculation, before presenting next a qualitative correlation between the experimental singlet-triplet values and a metrics used to measure the extent of that charge-transfer .
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 M. Moral-Muñoz, L. Muccioli, W.-J. Son, Y. Olivier, and J. C. Sancho-García, J. Chem. Theory Comput., submitted (2014)
Part II: Computing charge transport properties in organic semiconductors:
insights from molecular modeling at different length scales
Dr. Yoann Olivier (firstname.lastname@example.org)
Laboratory for Chemistry of Novel Materials
University of Mons, Belgium
Abstract: Improving the charge carrier mobility in organic-based devices such as LEDs, solar cells and FETs is of crucial importance in order to achieve standardized performances. To reach this objective, a detailed understanding at the molecular scale of the influence of structural organization on the charge carrier mobility is a key issue. In disordered materials, the hopping regime is a reliable model to depict charge transport. In this framework, charge transport has often been described using the semi-classical Marcus theory, with the main parameters - transfer integral and reorganization energy - calculated with quantum chemistry . In this contribution, we will highlight by means of molecular modeling the subtle interplay between the molecular organization and charge transport properties. By combining quantum-chemical methods, molecular dynamics and Monte Carlo simulations, we will show different examples going from crystalline  to disordered organic semiconductors such as liquid-crystalline  and polymeric materials  with special attention on the potential lessons learnt for further design of materials with improved charge transport properties.
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