Solid state lighting industry is booming in recent years because of the green energy requirement. Therefore, phosphorescent OLEDs using phosphorescent emitters doped into charge-transporting hosts as emissive layers (EMLs) have attracted extensive interest due to their highly efficient emission compared to conventional fluorescent OLEDs, through radiative harvesting of both electro-generated singlet and triplet excitons. To achieve better charge balance and device performance, many researchers focus on developing new phosphorescent host materials with bipolar charge transporting property. In this work, we successfully designed and synthesized a host material CzppT containing hole-transporting carbazole and electron-transporting pyridine and investigated the physical properties. With a high triplet energy, CzppT is considered a promising universal host material and has been applied to phosphorescent OLEDs of blue/white colors. Blue/white OLEDs based on CzppT as host and Firpic/Ir(piq)2(acac) as dopant materials show maximum external quantum efficiencies (11.0% for blue, 11.32% for white) and CIE coordinates [(0.18,0.41)for blue, (0.32,0.36) for white)]. The results indicate that the bipolar host CzppT with high triplet energy has potential in manufacturing blue and white OLEDs for display or lighting applications.

[pt] Neste trabalho é apresentado o estudo dos dispositivos orgânicos emissores de luz fosforescentes (PHOLED) baseados em compostos de baixo peso molecular. O estudo foi fundamentado nas análises dos complexos baseados no íon de Ir3+: [Ir(t-pzp)2pic] [fac-Ir(t-bupzp)3] e outros complexos já estudados anteriormente a base de Eu3+: [Eu(DBM)3PHEN] e [Eu(DBM)3DMSO2]. No desenvolvimento dos PHOLEDs, a dopagem de uma matriz orgânica com estes complexos reveste uma importância fundamental. Por tanto, como o intuito de estudar e analisar estes sistemas os complexos foram dopados com diversas concentrações em diferentes matrizes orgânicas. Os resultados obtidos revelaram que no caso dos complexos de Ir3+ os melhores valores da concentração do complexo encontram-se na faixa 13-15 porcento em peso. Já no caso dos complexos de íons de terra rara (Eu3+) as melhores concentrações devem ser superiores a 15 porcento em massa, para que ocorra uma transferência de energia eficiente e mantendo o espectro de emissão dos complexos resultando em um aumento da eficiência externa dos dispositivos. Neste trabalho foi desenvolvida também, uma metodologia que, combinando as técnicas de XRF e RBS, permite elaborar um gráfico de calibração para a determinação da concentração efetiva do dopante nos diferentes filmes co-depositados. Finalmente, para aumentar a eficiência dos PHOLEDs foi investigado o efeito da vibração do substrato durante a deposição térmica dos filmes. Os resultados indicam uma redução na densidade de aglomerados e na rugosidade, além de uma melhoria na homogeneidade dos filmes depositados. O aumento de 40 porcento na eficiência do dispositivo fabricados indica que a técnica de vibração é promissora para o desenvolvimento de dispositivos eficientes. / [en] This thesis reports the investigation of the phosphorescent organic light emitting devices (PHOLED) based on low molecular compounds. The study was carried out by analyzes the optical and electrical characteristics of thin films of Ir3+: [Ir(t-pzp)2pic] and [fac-Ir(t-bupzp)3] and other complexes based on Eu3+: [Eu(DBM)3PHEN] and [Eu(DBM)3(DMSO)2]. In developing of PHOLEDs, technology, the doping of an organic matrix with these complexes has a fundamental importance. Therefore, in order to investigate these systems Ir3+ and Eu3+ organic complexes were used as doping with a variety of concentrations in different organic matrix. The results revealed that in the case of Iridium complexes the best values are in the range 13-15 percent. On the other hand, for the rare earth complexes the best concentrations should be greater than 15 percent in order to obtain a efficient energy transfer preserving the emission spectrum of the complexes. Furthermore, the use of the doping results in an increased of the external efficiency of the device. In this work, a methodology combining the XRF and RBS techniques was also developed which allows the direct determination of the effective dopant concentration in co-deposited films through a calibration curve. Finally, to increase the efficiency of the PHOLEDs, the effect of mechanical vibration of the substrate on the thin films characteristics during the thermal deposition was investigated. The results indicate a reduction in the clusters density and film roughness, and an improved homogeneity of the deposited films. The 40 percent increase in efficiency of the devices fabricated under these conditions is a clear indication that the technology holds promise for the development of efficient devices.