| Summary: | 碩士 === 長庚大學 === 機械工程研究所 === 91 === Unlike traditional Liquid-Crystal Displays (LCDs), Organic Light Emitting Devices (OLEDs) are self-luminous and need no backlighting. Despite these advantages, OLEDs are not widely commercialized due to its short operation lifetime. In this thesis, the lifetime mechanism in OLEDs, where the device structure based on a mixed emitting layer (EML), is investigated in terms of carrier transport and direct holes-electrons recombination. The mixed EML is sandwiched between the hole and electron transport layers. From accelerated degradation tests, the operation lifetime of optimal mixed layer (ML) device is considerably improved over the heterojunction (HJ) OLEDs, which shows the lifetime of about 60 h with initial luminance of 10,000 cd/m2. This significant improvement in device lifetime is attributed to the elimination of the organic-organic interface. In addition, the luminance reaches 244,100 cd/m2 at 8V, which corresponds to a luminous efficiency of 4.34 cd/A. These results demonstrate that the mixed EML can extend the performance of OLEDs without significantly changing the device structure or organic material.
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