Several results were reviewed on the charge injection into thin conjugated polymer films. The space charge limited tunneling current (SCTC) and space-charge limited current (SCLC) models were used to explain the charge injection and transport in conjugated polymer films such as those used in organic light emitting diodes. On the basis of regional approximation, the effect of the space charge on the current density of electrons tunneling from metal electrodes to the lowest unoccupied molecular orbital of a polymer film is calculated. The space charge is considered to decrease with increasing distance of the injecting electrode. If the space charge occupies only a limited region between the tunneling (short) distance and the collecting electrode, the current (I) is found to be independent on a power law of the applied voltage (V). However, if the space charge occupies all the region between the tunneling distance and the collecting electrode, I is found to vary exponentially on V for lower V values, and that follow approximately the law of Child at high V in region I, the law of Trap filled limited current at middle voltage in region II and the region III show Ohm¡¦s law at lower voltage. The space charge limited tunneling current (SCTC) theory gives the same results of the space charge limited conduction theory when the energy barrier for charge carrier injection is small or when the polymer layer is thick. Under various bias voltages, the charge transport mechanism was analyzed to investigate the effects on the thin conjugated polymer films induced by the parameters such as background concentration, trap-state density and space charge etc... The results show the transport current decrease with increasing the trap-state density and also increase the characteristic temperature parameters. In this study, the regional approximation is applied to calculate the charge injection and current transport mechanism in the organic thin film. The SCTC and SCLC models are compared to the experimental data. It shows that there is a good agreement between theory and experiment, concerning both current magnitude and current versus voltage dependence. It is very important that our model gave a new way to simplify the calculation and to discuss the charge transport of organic light emitting diode.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Esta dissertação levanta uma análise comparativa dos processos políticos que antecederam a construção de duas pontes transnacionais nas Américas: a ponte sobre o Rio Tacutu, que liga as cidades de Lethem (Região 9, Guyana) e Bonfim (Roraima, Brasil); e a ponte sobre o Rio Hondo, que liga as cidades de Santa Elena (Corozal, Belize) e Subteniente López (Quintana Roo, México). Enquanto isso, o estudo inserese no corpo mais amplo de pesquisas que analisam o processo de integração das Américas através do uso de infraestrutura física. Além disso, a pesquisa aborda a maneira em que poderes emergentes usam infraestrutura para propósito de projeção de poder regional nos seus entornos geopolíticos, particularmente, em relação aos seus vizinhos contíguos menores. Esta análise realiza-se no contexto histórico do reconhecimento da necessidade de fomentar integração entre os países do sul global e de países de tradições coloniais diferentes; e mais ainda, visa alcançar essa meta com o uso da infraestrutura física. Metodologicamente, é um estudo interpretativo quantitativo das fontes bibliográficas e discursos executivos, utilizando o método comparativo para deduzir modos de interação entre dois poderes emergentes latinoamericanos e dois países relativamente pequenos e isolados do Caribe anglófono. Pode-se concluir que as duas pontes foram construídas e inauguradas dentro de projetos mais amplos para integração regional, promovidos pelo México e Brasil, para as regiões imediatas de influência geopolítica, facilitado por fortes vínculos bilaterais históricos no campo de segurança de território; e completado pela transição contemporânea dos países caribenhos na busca para novos parceiros internacionais, frente à perda de viabilidade de vínculos tradicionais. / This dissertation carries out a comparative analysis of the political processes leading up the construction of two transnational bridges in the Americas; these are the Takutu River Bridge linking Lethem, Region 9, Guyana and Bonfim, Roraima, Brazil; and the Hondo River Bridge linking Santa Elena, Cozoral, Belize and Subteniente López, Quintana Roo, Mexico. In so doing, the study is inserted in a wider body of researches that analyse the process of integration in the Americas through the use of physical infrastructure. The research further highlights how emerging powers use infrastructure as a means of regional power projection in their geopolitical spaces, particularly as it pertains to smaller contiguous neighbours. This analysis takes place in the historical context of countries of the global south and of different colonial traditions, recognising the need to foster integration, and achieve advancement in this regard through infrastructure. Methodologically, it is an interpretive qualitative study of bibliographical sources and executive speeches, using the comparative method to deduce modes of interaction between two emerging Latin American powers and two relatively small and isolated continental countries of the Anglophone Caribbean. It may be concluded that the two bridges were successfully constructed and inaugurated as part of wider projects for regional integration fostered by Mexico and Brazil for their regions of immediate geopolitical influence, and aided by historically strong bilateral relations in the area of territorial integrity and further, the contemporary transitioning in the search by Caribbean countries for new international partners as old linkages become less viable.