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Doctoral Thesis
DOI
10.11606/T.59.2004.tde-30112004-152626
Document
Author
Full name
George Barbosa da Silva
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Ribeirão Preto, 2004
Supervisor
Committee
Graeff, Carlos Frederico de Oliveira (President)
Fonseca, Fernando Josepetti
Mulato, Marcelo
Pela, Carlos Alberto
Zanatta, Antonio Ricardo
Title in Portuguese
Ressonância magnética detectada eletricamente em diodos de Alq3
Keywords in Portuguese
Alq3
diodo eletroluminescente
éxciton
ressonância
RMDE
Abstract in Portuguese
Ressonância magnética detectada eletricamente (RMDE) de banda-X (9 GHz) e de banda-K (24 GHz) foram usadas para estudar diversos diodos baseados em tris-8(hidroxiquinolinolato) de alumínio III (Alq3). A técnica de RMDE consiste, basicamente, em medir a variação da condutividade quando o sistema entra na condição de ressonância magnética; assim, é possível relacionar propriedades de transporte elétrico com as funções de onda das moléculas envolvidas no processo. Para este estudo foram confeccionados diodos eletroluminescentes e unipolares de multicamadas no Laboratoire d'Optoélectronique des Materiaux Moléculaire (LOMM), da École Polytechnique Fédérale de Lausane (EPFL), Suíça, pelo Dr. Frank Nüesch. Faz parte também deste trabalho a montagem experimental do sistema de RMDE de banda-K, onde a maior parte dos dados foram obtidos. O sinal de RMDE dos diodos unipolares, da ordem de 1E-6, é atribuído ao processo dependente de spin de saltos eletrônicos que ocorre próximo às interfaces. O sinal típico de RMDE dos diodos eletroluminescentes é mais intenso, da ordem de 1E-4, e é atribuído à ressonância de spin-1/2 na formação dos éxcitons. O espectro de RMDE, por meio de ajuste de curvas, pôde ser decomposto em duas gaussianas: uma com largura de linha pico-a-pico DHPP de 1,6 mT, independente do campo elétrico aplicado no dispositivo, e outra variando de 2,0 mT a 3,4 mT. A componente mais estreita se deve à ressonância do radical positivo de Alq3, enquanto que a componente mais larga àquela do negativo. O estudo da forma de linha e de sua dependência com o campo elétrico dos espectros de RMDE de diodos unipolares dão suporte à ambas as atribuições. Neste trabalho, a questão da eficiência quântica e da zona de recombinação também são discutidas.
Title in English
Electrically detected magnetic resonance of Alq3 based diodes
Keywords in English
Alq3
EDMR
exciton
OLED
resonance
Abstract in English
Electrically Detected Magnetic Resonance (EDMR) at X-band (9GHz) and K-band (24 GHz) were used to investigate Alq3 based diodes. EDMR technique consists basically of measuring conductivity variation at magnetic resonance conditions; thus, it is possible to correlate electrical transport properties with wave functions of the molecules involved in the process. Electroluminescent and unipolar multilayer diodes were prepared in the Laboratoire d'Optoélectronique des Materiaux Moléculaire (LOMM), at on École Polytechnique Fédérale de Lausane EPFL, Switzerland by Dr. Frank Nüesch. The experimental setup of the K-band EDMR system, where most of the data were obtained, was also part of this work. The unipolar diodes EDMR signal is of the order of 1E-6 and is attributed to spin dependent hopping process close to the interfaces. The electroluminescent diodes typical EDMR signal is more intense, of the order of 1E-4 , and is attributed to exciton´s formation spin-1/2 resonance. The EDMR spectrum can be decomposed into two Gaussians: one with peak-to-peak line width (DHPP) of 1.6 mT, independent of the electrical field applied to the devices, and other one whit DHPP of 2.0 mT to 3.4 mT. The narrower component is due to the resonance of positive Alq3 radical, while the larger component is due to the negative. Both attributions are supported by the investigation of line shape and its dependence of electrical field in the unipolar diodes EDMR spectra. In this work, the quantum efficiency and the recombination zone issues are also discussed.
 
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RMDE-Alq3.pdf (1.15 Mbytes)
Publishing Date
2004-12-01
 
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