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| Author(s): |
George Barbosa da Silva
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Ribeirão Preto. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (PCARP/BC) |
| Defense date: | 2004-09-02 |
| Examining board members: |
Carlos Frederico de Oliveira Graeff;
Fernando Josepetti Fonseca;
Marcelo Mulato;
Carlos Alberto Pela;
Antonio Ricardo Zanatta
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| Advisor: | Carlos Frederico de Oliveira Graeff |
| Abstract | |
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. (AU) | |