The accomplishments presented in this thesis are the development of three models for simulation of space charge generation in the phosphor layer of alternating current thin-film electroluminescent (ACTFEL) devices and the results from simulation of these models. First, a single sheet charge model is developed and simulated. The single sheet charge model is a model that simplifies the problem of modeling an arbitrary distribution of space charge across the phosphor layer by lumping all of the space charge into a sheet of charge at a specified location in the phosphor layer. In this model and all subsequent models, space charge creation is assumed to occur by field emission from bulk traps or by impact ionization of deep-level traps. A fairly exhaustive parametric variation study of the single sheet charge model is performed and the results are presented and discussed. The results show space charge effects that are quite dependent on several parameters such as the number of bulk traps in the phosphor layer, the location of the sheet of charge, the capture efficiency for space charge annihilation, and the characteristic field for impact ionization of the deep-level traps. The second model considered is a logical extension of the single sheet charge model, the two sheet charge model, which models the space charge distribution as two sheets of charge rather than one. This model has potential application in the simulation of ACTFEL devices which exhibit large and/or symmetrical space charge effects. The final model developed is an equivalent circuit/SPICE model of the single sheet charge model. Actually, two models are developed, one for space charge creation by field emission and one for impact ionization of deep-levels. Two SPICE models are required because of functional differences in the dependencies of space charge creation. The results of a simulation showing overshoot generated by SPICE are given for the field emission equivalent circuit. / Graduation date: 1996

No description available.

No description available.

Thesis (Ph.D.)--McMaster University (Canada), 1991. / Source: Dissertation Abstracts International, Volume: 54-02, Section: B, page: 1040.

Thesis (M. S. in Interdisciplinary Materials Science)--Vanderbilt University, Aug. 2008. / Title from title screen. Includes bibliographical references.

Thesis (Ph.D.)--University of Western Australia, 2006.

Thesis (M.S.)--Oregon State University, 1992. / Typescript (photocopy). Includes bibliographical references (leaves 82-85). Also available on the World Wide Web.

Thesis (Ph.D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2008. / Committee Chair: Tolbert, Laren; Committee Member: Collard, David; Committee Member: Lyon, Andrew; Committee Member: Srinivasarao, Mohan; Committee Member: Wilkinson, Angus

Submitted by Renan Colucci null (37412942840) on 2016-07-12T19:19:53Z No. of bitstreams: 1 dissertação_RENAN_versãofinal.pdf: 3242692 bytes, checksum: c7bf17a6e3f70f7b97cb6c8ecfa1e065 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-07-15T16:29:02Z (GMT) No. of bitstreams: 1 colucci_r_me_rcla.pdf: 3242692 bytes, checksum: c7bf17a6e3f70f7b97cb6c8ecfa1e065 (MD5) / Made available in DSpace on 2016-07-15T16:29:02Z (GMT). No. of bitstreams: 1 colucci_r_me_rcla.pdf: 3242692 bytes, checksum: c7bf17a6e3f70f7b97cb6c8ecfa1e065 (MD5) Previous issue date: 2016-06-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Atualmente é possível fabricar dispositivos eletroluminescentes (EL) utilizando como material ativo uma dispersão de um pó eletroluminescente inorgânico em uma matriz polimérica condutora. Entretanto, esses materiais são quimicamente instáveis, o que impede a deposição de alguns materiais solúveis sobre eles, como por exemplo, eletrodos de tinta prata. Para solucionar este problema, desenvolvemos uma matriz condutora e quimicamente estável formada pelo polímero condutor poli(3,4-etileno dioxitiofeno):poliestireno sulfonado (PEDOT:PSS) e pelo material sílica-orgânico 3-glicidoxipropil trimetilsilano (GPTMS). Foram produzidos compósitos de PEDOT:PSS/GPTMS com diversas concentrações de PEDOT:PSS, com os quais foram produzidos filmes uniformes, insolúveis e com condutividade elétrica entre 2 S/cm e 400 S/cm. A dependência da condutividade elétrica destes materiais em função da temperatura e da concentração de PEDOT:PSS foi descrita pelo modelo de transporte de cargas variable range hopping (VRH-3D). Adicionando-se o material eletroluminescente (EL) inorgânico silicato de zinco dopado com manganês (Zn2SiO4:Mn) à matriz condutora de PEDOT:PSS/GPTMS foi obtido um compósito para a produção de dispositivos EL. Depositando-se este compósito EL sobre substratos de vidro contendo eletrodos transparentes de óxido de estanho e índio, foram obtidos dispositivos EL com tensão de operação de 30 V e eficiência luminosa de 1,3 cd/A. Além disso, a transmitância óptica e a resistência de folha de filmes do compósito condutor (PEDOT:PSS/GPTMS) foram avaliadas, demonstrando que este material apresenta propriedades compatíveis com a aplicação como eletrodo transparente. Por fim, foram produzidos dispositivos EL utilizando o compósito condutor PEDOT:PSS/GPTMS como eletrodos e o compósito EL PEDOT:PSS/GPTMS/ Zn2SiO4:Mn como material ativo. Com este experimento, foi demonstrada a possibilidade de fabricar dispositivos EL por rota líquida, onde o compósito PEDOT:PSS/GPTMS foi utilizado tanto para a fabricação dos eletrodos como para a produção do material ativo do dispositivo. / It is possible to fabricate light-emitting (LE) devices with LE composites as active material. These light-emitting composites are produced with a LE inorganic powder dispersed into a conducting polymer matrix. However, these composites are chemically unstable, limiting the deposition of soluble materials over it. To overcome this problem we developed a high-stability conductive matrix comprising the conductive polymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and the organic-silicate 3-glycidyloxypropyl)trimethoxysilane (GPTMS). Composites PEDOT:PSS/GPTMS with diverse weight concentrations of PEDOT:PSS were produced and used to fabricate high-stability films with electrical conductivity from 2 S/cm up to 400 S/cm. The charge transport in these conductive composites were studied as function of the temperature, as well as of the PEDOT:PSS concentration, and described by the 3D variable range hopping model. A light-emitting composite was produced adding to this conductive composite the inorganic electroluminescent powder Mn-doped zinc silicate (Zn2SiO4:Mn). Light-emitting devices, with turn-on voltage of 30 V and luminous efficacy of 1.3 cd/A, were produced with a coating of the developed LE composite done over glass substrates containing indium tin oxide transparent electrodes. Additionally, the optical transmittance and sheet resistance of films produced with the conductive composite PEDOT:PSS/GPTMS were evaluated showing that this material is suitable to fabricate transparent electrodes. Finally, were produced light-emitting devices employing the conductive composite PEDOT:PSS/GPTMS as electrodes and the light-emitting composite PEDOT:PSS/GPTMS/ Zn2SiO4:Mn as active material. This experiment has shown the fabrication of solution-processed light-emitting devices using the composite PEDOT:PSS/GPTMS as transparent electrode and as component of the active material.

Organic light-emitting diodes (OLEDs) have been considered as the future lighting and display system and rapidly growing since 1987. It has been already used in many commercial applications such as OLED televisions, cell phone displays, and lighting systems. The OLED has higher luminous efficiency and extremely thinner layer compare to any other lighting devices, also it has flexibility and self-emission. However, there are still some drawbacks for the device performances such as lifetime especially on blue organic films, cost of manufacturing process, and moisture that we need to work on before wide-scale commercialization like LCD or LED. This thesis has focused on developing a charge distribution such as deriving empirical equations in multi-emissive layer OLED, improving external quantum efficiency (EQE) and lowering roll-off. Key results are summarized as follows: (1)We seek to establish a quantitative method to estimate the holes and electrons ratio in the recombination zones. The result shows a trend in the charge recombination ratio depending on the hole and electron transport layer (HTL/ETL) thickness. We obtained an empirical relationship between electron/hole transport layer thicknesses and emission ratio in emissive layer (EML). In addition, the electroluminescence (EL) spectra were analyzed by fitting a Gaussian distribution for the two emissive layers to calculate the intensity ratio of the energy transitions. The arrival time of hole and electrons from each electrode was determined using the thickness and mobility of NPB as hole transport layer and TPBi as electron transport layer. From these initial results, we derived an empirical mechanism to meet with an exponential relationship that can allow us to design custom- made OLEDs. (2)We fabricated White OLEDs in which the emissive layers are chemically doped with blue and red fluorescent dopants of BUBD-1 and DCJTB. This work continues by estimating of emission ratio between red and blue emissive layers by changing the thicknesses of HTL and ETL. The recombination of charge carriers was first identified the location and then we derived an empirical equation for peak intensity ratio of EL spectra with respect to thickness of the HTL/ETL to determine how recombination zone depends on the HTL and ETL thickness. The EL spectra of WOLEDs were fitted with a Gaussian distribution for the two emissive layers using host-dopant system and intensity ratio of blue and red emission peak is 61:39 when thickness of HTL and ETL are 80nm and 20nm, respectively. Also, this intensity ratio of blue and red emission peak (61:39) has the CIE color coordinates of (0.34, 0.40). We obtained a preliminary relationship between thickness of electron/hole transport layer and ratio of two emission peaks. (3)The improved external quantum efficiency (EQE) and reduced roll-off properties of blue phosphorescent organic light-emitting diodes (PHOLEDs), were obtained with structure, ITO/NPB (40 nm)/TCTA (20 nm)/mCP:FIrpic (7%)(30 nm)/TPBi (30 nm)/Liq (2 nm)/Al (80 nm) by incorporating a TCTA inter-layer. We compared the properties of BCP and TPBi as the ETL with a typical structure of HTL/ EML/ETL in OLEDs and utilized inter-layer in the optimized structure to enhance EQE to 52% at 5.5 V, also stabilize the roll-off of 63%. The use of inter-layer in blue PHOLEDs exhibits a current efficiency of 10.04 cd/A, an EQE of 6.20% at 5.5 V and the highest luminance of 10310 cd/m2 at 9.5 V.