Tham khảo tài liệu 'organic light emitting diode part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Material Issues in AMOLED 53 Fig. 10. Molecular structure and calculated dipole moment of Phenanthroline series ETMs Device fabrication and characteristics All OLEDs were fabricated on indium tin oxide precoated onto glass substrate. Organic layers were vacuum deposited via thermal evaporation in the high-vacuum chamber. Fig. 11 shows the structure of blue OLED device and its energy diagram. The thickness and materials of each layer are same for fabricated devices except ETMs to eliminate another possible luminance attenuating factor. Fig. 11. Blue OLED structure and Energy diagram The IVL current density applied voltage luminance characteristics of OLEDs were measured using a Photo Research Inc. PR-650 spectrometer. The operational life-time characteristics were determined from a series of measurements of changes in luminance and drive voltage as function of time under DC driving conditions. 54 Organic Light Emitting Diode Devices performance properties depended on ETMs and their ability to transport electron 29 . Fig. 12 and Fig. 13 showed I-V and L-Efficiency characteristics of ADN series ETMs respectively. Regardless of dipole moment differences device performances depended on the electron transporting ability of the hetero-aromatic rings attached to ADN backbone and similar property tendency was observed when we applied those hetero-aromatic rings to another framework before. ET4 quinoline moiety gave the best electron transporting performance but ET2 iso-quinoline showed poor electron transporting ability. In spite of different electronic structures of hetero-aromatic rings Pyrimidine ETl and pyridine ET3 moieties exhibited similar properties. Similar to the results of the ADN series ETMs it was difficult to explain the result in dipole moment aspect and device performance characteristics mainly due to the property of phenanthroline stacking. ET7 and ET8 are simple structure with minimum appendages and almost flat 3-D structure so they can be .
