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Organic Light Emitting Diode Material Process and Devices Part 12

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Tham khảo tài liệu 'organic light emitting diode material process and devices part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 266 Organic Light Emitting Diode - Material Process and Devices FOLED 10 were thought to have a lower electric and brightness properties than FOLED 0 . Although the sheet resistance of 16 mm bent ITO is 230 Q this value is sufficiently small for using electrode in OLEDs. Gu et al. 1996 Fig. 31. Changes of the sheet resistance after the bending test of ITO films. Fig. 32 showed the SEM images of the ITO surface as a function of the variation radius of curvature. The crack phenomenon of bent ITO was appeared from the lowered radius of bending test 16 mm. The ITO for the bending test at 13 mm and 10 mm radius showed the rough surface and a large amount of crack from the whole area. In our case the bent ITO at 16 mm 13 mm and 10 mm have the hasty reductive properties such as sheet resistance and surface morphology. In this result the reasons for reduced properties of bent FOLEDs are follows. Firstly the bent FOLEDs have lowered device characteristics such as increased driving voltage and decreased luminance property because of the increase resistance of bent ITO by a bending test in radius of below 16 mm. Chen et al. 2002 Secondly many attempts have been focused on interface property between an organic and electrode layer. The OLEDs using the ITO anode with smooth surface have shown superior device properties as lower turn-on voltage and higher luminescent efficiency because these devices are improved contact property. In this study the bent FOLEDs have shown inferior device performance because rough surface of the bent ITO was decreased contact property in the interface between the TPD organic layer and ITO electrode. Kwon et al. 2002 In conclusions we fabricated FOLEDs with an ITO anode a TPD hole transport layer an Alq3 emitting layer and an Al cathode deposited on the PET substrate and studied FOLEDs characteristics after bending test at various radiuses of 10 mm 13 mm 16 mm and 19 mm. The performance of FOLEDs with lowered radius 16 mm was decreased the device .