The Fabrication of Blue Organic Light Emitting Diode with Stacked Multi-Emission Layers Structure

• Main Authors: Shih-Chin Lin, 林士欽
• Other Authors: Meiso Yokoyama
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/24587436571537194613

碩士 === 義守大學 === 電子工程學系 === 92 === In this investigation, we fabricated OLEDs with a multi-emission layer structure stacked by NPB/MTDATA. Firstly, we studied the effect of NPB and MTDATA thickness, respectively, on the properties of devices with the structure ITO/ MTDATA(200Å)/ NPB[(600-X-Y)Å)/ MTDATA(YÅ)/ NPB(XÅ)/ BCP (150Å)/ Alq(250Å)/ LiF(7Å)/ Al. We found the devices with thickness of NPB and MTDATA are both 100Å possess the optimum properties. It implies that the thickness ratio of NPB and MTDATA is 1 in a stacked multi-emission layer(SMEL) OLED will provide a optimal characteristic. Then we studied the photoelectronic properties of devices with double SMEL OLEDs. The device’s structure is ITO/ MTDATA(200Å)/ NPB(200Å)/ [MTDATA(100Å)/ NPB(100Å)]n=2/ BCP(150Å)/ Alq(250Å)/ LiF(7Å)/ Al. Furthermore, we fabricated SMEL OLEDs by dividing the emission layer. The thickness ratio of NPB and MTDATA in SMEL maintains 1. The structure is ITO/MTDATA(200Å)/NPB(200Å)/[MTDATA(200/nÅ)/NPB(200/nÅ)]n/BCP (150Å)/Alq(250Å)/ LiF(7Å)/Al. The device shows optimum properties when the number(n) is 3. We also studied the mechanism which improves the luminance efficiency of devices. There are two mechanisms which may improve the luminance efficiency. Firstly, several energy wells produced by the difference of the lowest occupied molecular orbit (LUMO) between NPB and MTDATA will capture the electrons in the NPB layer and they recombine with holes. Electron-hole recombination zone is dispersed by the exise of energy wells and luminance efficiency can be improved. Secondly, the SMEL in the structure may decrease the mobility of holes to balance the amount of electrons and holes at the NPB/BCP interface. It will improve the luminance efficiency of devices. For confirming the first mechanism, we doped rubrene into NPB of SMEL to observe whether there are carriers recombine in the NPB layer to generate the light from rubrene.