EL PROGRAMA DE POSGRADO EN FÍSICA invita a todos para lo seminario:

  Effect of singlet triplet recycling in the charge transfer state manifold and molecular geometry on thermally activated delayed fluorescence  

Prof. Andy P. Monkman

Dept. of Physics, Durham University, South Road Durham, UK

Resumen:

Figure 1: Temperature dependent delayed fluorescence measurements of a near zero exchange energy ICT TADF

Detailed photophysical measurements of intramolecular charge transfer states have been made both in solution and solid state¹. Temperature dependent emission and delayed emission are used to map the energy levels involved in molecule decay, and through detailed kinetic modelling of the thermally activated processes observed, true electron exchange energies and other energy barriers of the systems determined.

For specific donor acceptor molecular configurations, the CT singlet and triplet states are found to be the lowest lying excited states of the molecule with very small electron exchange energies = kT. In these cases the decay kinetics of the molecules become significantly different to normal molecules, and the effect of rapid recycling between CT singlet and triplet states is seen to greatly extend the lifetime of the ‘excited state’ and yield non-exponential decay. Quantum yields increase markedly, even though the intersystem crossing rate is fast, ? 10⁹ s^-1. The decay kinetics is found to be very sensitive to both temperature and sample inhomogeneity², see figure 1. Temperature dependent delayed emission measurements reveal very different time domain behaviour and the effects of ICT emitter inhomogeneity is revealed. Clear evidence will be given to show that TADF reaches 100% efficiency at harvesting triplet states^1,3, and device having > 15% EQE discussed.

 We will then go on to show the results for an ICT molecule with highly controlled structure i.e. the donor and acceptor fragments are held rigidly orthogonal. In this molecule the CT states can clearly be seen to be the lowest energy states of the molecule with a very small exchange energy (singlet triplet gap). Here we find that there are substantial differences between optical and electroluminescent photophysics resulting in device being far more efficient than is suggested by the molecules PLQY. For the first time we can show that the PLQY of the emitter is not the figure of merit to use in a device, because the excited states are formed in a different way within the device which avoids a major excited state quenching mechanism. This will be discussed in a new molecule that has a PLQY of 30% but gives devices having >19% EQE.

 TADF thus not only enables 100% of triplet states to be harvested, the charge transfer states which give rise to emission and TADF also enable more efficient singlet emission than ‘PLQY’ would lead us to believe.

 References

 1    V. Jankus, C. J. Chiang, F. Dias, and A. P. Monkman, Adv Mater 25, 1455 (2013).

2    F. B. Dias, K. N. Bourdakos, V. Jankus, K. C. Moss, K. T. Kamtekar, V. Bhalla, J. Santos, M. R. Bryce, and A. P. Monkman, Adv Mater 25, 3707 (2013).

3    D. Graves, V. Jankus, F. B. Dias, and A. Monkman, Adv Funct Mater 24, 2343 (2014).

4      Vygintas Jankus, Przemyslaw Data, David Graves, Callum McGuinness, Jose Santos, Martin R. Bryce, F. B. Dias, and A. P. Monkman, Advanced Functional Materials 24, 6178. (2014).

Fecha: 24 de abril de 2015 – (viernes) – Lugar: Sala 212 Auditorio del Departamento de Física – Horário: 10h15min

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EL PROGRAMA DE POSGRADO EN FÍSICA invita a todos para lo seminario:

  Detection of quantum entanglement: experiments with spatially entangled photon pairs  

Stephen Patrick Walborn

Instituto de Física – UFRJ

 Resumen:

 The twin photons produced by spontaneous parametric down-conversion have been an exceptional tool for the study of entanglement and quantum information. The spatial correlation of these photons was one of the first properties to be studied. Nevertheless, the convenient and efficient detection of quantum entanglement in the spatial variables is still an active area of research, with possible applications in quantum cryptography and communication. Here we present several experiments performed at the Quantum Optics Laboratory at the Instituto de Física, Universidade Federal do Rio de Janeiro. We present several novel experimental methods to detect the entanglement in the transverse spatial variables of photon pairs. Both methods use spatial light modulators to imprint an appropriate phase profile on the down-converted photons. Our first method uses this phase profile to measure the spatial correlation functions directly. With these, we can evaluate known entanglement witnesses in a more efficient fashion, without the need for a position-dependent detection system. Our second method uses complementary masks to discretize the detection system, again allowing for a more efficient identification of entanglement via a novel entanglement witness.

Fecha: 17 de abril de 2015 – (viernes) – Lugar: Sala 212 Auditorio del Departamento de Física – Horário: 10h15min

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 EL PROGRAMA DE POSGRADO EN FÍSICA invita a todos para lo seminario:

  O Lado Escuro do Universo   

Rogerio Rosenfeld – Instituto de Física Teórica / UNESP

Resumen:

Sabemos hoje que apenas 5% do Universo é composto de átomos. Nesse colóquio vou descrever brevemente o que pensamos que são os 95% restantes: matéria escura e energia escura.

Fecha: 10 de abril de 2015 – (viernes) – Lugar: Sala 212 Auditorio del Departamento de Física – Horário: 10h15min

 El programa de Posgrado en Fisica invita a todos para la:

  Sustentación de Tesis

 Marcos João Correia

 ESTUDO DE NANOPARTÍCULAS MAGNÉTICAS ATRAVÉS DE SIMULAÇÕES COMPUTACIONAIS

Jurados:

 Prof. Dr. Wagner Figueiredo – (presidente) – FSC/UFSC

Prof. Dr. Walther Schwarzacher – (miembro externo) – University of Bristol

Drª. Sueli Hatsumi Masunaga – (miembro externo) – USP/IF

Prof. Dr. Nilton da Silva Branco – (membro titular) – UFSC/FSC

Prof. Dr. Lucas Nicolao – (miembro titular) – UFSC/FSC

Prof. Dr. Marcelo Freitas de Andrade – (miembro titular) – UFSC/Araranguá

Prof. Dr. Marcus Emmanuel Benghi Pinto – (miembro suplente) – UFSC/FSC

Fecha: 9 de abril de 2015 – jueves – Horario: 9:30 am – Lugar: Sala 212 – Auditorio del Departamento de Física

El Programa de Posgrado en Física invita a todos para:

Examen de Cualificación al Doctorado

 Carlos Gentil Oro Lemos

 TEOREMAS DE FLUTUAÇÕES APLICADOS A MODELOS MAGNÉTICOS

Jurados

 Prof. Dr. Wagner Figueiredo – (presidente) – FSC/UFSC

Prof. Dr. Masayuki Oka Hase – (miembro externo) – USP

Prof. Dr. Eduardo Inacio Duzzioni – (miembro titular) – UFSC/FSC

Prof. Dr. Eduardo Cerutti Mattei – (miembro titular) – UFSC/FSC

Prof. Dr. Lucas Nicolao – (miembro suplente) – UFSC/FSC

 Fecha: 2 de abril de 2015–quinta-feira– Horario: 10:00 am – Lugar: Sala 114 – Sala de Reuniones del Departamento de Física

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El programa de Posgrado en Física invita a todos para la:

 Sustentación de Disertación

 Giovanni Formighieri

 O ESPAÇO-TEMPO DE UM DIPOLO MAGNÉTICO

Jurados

 Prof. Dr. Celso de Camargo Barros Junior – (presidente) – UFSC/FSC

Prof. Dr. Marcelo Dalagnol Alloy – (miembro externo) – UFFS/Chapecó

Profª. Drª. Débora Peres Menezes – (miembro titular) – UFSC/FSC

Prof. Dr. Eduardo Cerutti Mattei – (miembro titular) – UFSC/FSC

Fecha: 31 de marzo de 2015 – martes- Horario: 5:00 pm – Lugar: Sala 201 – Sala de Reuniões do Programa de Pós-Graduação em Física

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