Seminário (extra) com a Profa. Dra. Christel M. Mariana – 10 de outubro de 2023 (terça-feira) – 10h15min
O PROGRAMA DE PÓS-GRADUAÇÃO EM FÍSICA convida para o seminário:
Phosphorescent vs. Fluorescent OLED Emitters: A Quantum Chemical Perusal
Profa. Dra. Christel M. Mariana
Department of Chemistry, Heinrich-Heine-University, Düsseldorf, Germany
Abstract: Electrons and electron holes carry spin angular momenta of ½. Upon recombination in electroluminescent devices, the electron–hole pairs statistically create 25% singlet excitons and 75% triplet excitons. For reaching 100% internal quantum efficiency in an organic light-emitting diode (OLED), singlet as well as triplet excitons need to be harvested for luminescence. One strategy for achieving this goal engages heavy transition metal complexes, typically Ir or Pt compounds, as phosphorescent emitters.[1,2] Recently, efforts were made to replace these precious metals by more earth-abundant elements. Metal-free organic donor–acceptor compounds and the coinage-metal coordination complexes, employed in third-generation OLEDs, emit thermally activated delayed fluorescence (TADF) instead of phosphorescence.[3] Understanding the underlying mechanisms is a key step toward the design and optimization of second- and third-generation OLED emitters. [4,5] We use combined density functional theory (DFT) and multireference configuration interaction (MRCI) methods to explore electronically excited states of small-molecule OLED emitters and their photophysical properties. Scalar relativistic effects are included via effective core potentials. Spin–orbit coupling is introduced in a second step, either perturbationally for determining rate constants of intersystem crossing (ISC) and reverse intersystem crossing (rISC) or variationally for obtaining phosphorescence rate constants. Modeling the photophysics of TADF emitters requires going beyond the Franck–Condon approximation. To this end, an efficient computational tool box has been developed in our laboratory. [6-9] After a brief introduction, our quantum chemical protocol and its application to some typical phosphorescent or TADF-emitting OLED dyes will be presented.
References
1. M. E. Thompson, MRS Bull. 32 (2007) 694– 701; 2. H. Yersin, A. F. Rausch, R. Czerwieniec, T. Hofbeck, T. Fischer, Coord. Chem. Rev.255 (2011), 2622– 2652 3. H. Yersin (Ed.), Highly Efficient OLEDs, Materials Based on Thermally Activated Delayed Fluorescence. Weinheim: Wiley-VCH (2018). 4. T. Penfold, E. Gindensperger, C. Daniel, C. M. Marian Chem. Rev. 118 (2018) 6975-7025 5. C. M. Marian, Annu. Rev. Phys. Chem. 72, 617 (2021) 6. C. M. Marian, A. Heil, M. Kleinschmidt, WIREs Comput. Mol. Sci. 9 (2019) e1394 7. M. Kleinschmidt, J. Tatchen, C. M. Marian, J. Chem. Phys. 124 (2006) 124101 8. M. Etinski, V. Rai-Constapel, C. M. Marian, J. Chem. Phys.140 (2014) 114104 9. M. Bracker, C. M. Marian, M. Kleinschmidt, J. Chem. Phys. 155, 014 102 (2021)
Data: 10 de outubro de 2023 (terça-feira) – Horário: 10h15min
Local: Auditório do Departamento de Química
Agenda de Seminários: https://ppgfsc.posgrad.ufsc.br/seminarios/
