串聯式有機發光二極體之研究

本研究以綠色螢光於有機發光元件，使用Alq3螢光主發光材料，作為單層式發光元件(EL, electroluminescence)，其結構為ITO/TAPC(30nm)/Alq3(60nm)/LiF(0.7nm)/Al(150n m)，於電流密度50 mA/m2，驅動電壓為8.2伏特，電流效率為2.95 cd/A。將此綠色螢光結構直接作串聯式堆疊連接，其結構為ITO/EL/EL/LiF(0.7nm)/Al(150nm)，發現於電流密度50 mA/m2，驅動電壓為17.3伏特，但電流效率為1.24 cd/A，因元件直接堆疊使得內阻抗變大，電子、電洞不易進入元件中。為提升電流注入效果，於兩EL之間加入電荷產生層(CGL, charge generation layer)，先使用P-type材料(MoO3)與TAPC共摻雜方式，改變摻雜比例與厚度調整，利用MoO3材料本身會產生電洞之特性，提高電流注入能力，增加電流效率，其結構為ITO/EL/TAPC:MoO3(10nm、30%)/EL/LiF(0.7nm)/Al(150n m)，於電流密度50 mA/m2，驅動電壓為15.2伏特，電流效率為3.22 cd/A。其次，加入N-type材料(C60)，可使電子與電洞注入於元件之平衡，且調整電荷產生層之厚度，其結構為ITO/EL/C60(10nm)/MoO3(4nm)/TAPC:MoO3(10nm、30%)/EL/LiF(0.7nm)/Al(150nm)，於電流密度50 mA/m2，驅動電壓為16.1伏特，電流效率為3.53 cd/A。最終，本研究以LiF(0.5nm)/C60(10nm)/MoO3(4nm)/TAPC:MoO3(10nm、30%)作為CGL層，於電流密度50 mA/m2，驅動電壓為16.7伏特，電流效率為4.23 cd/A，使用串聯式發光元件相較於單層式發光元件，可提升1.43倍的效果，且相同電流密度下，串聯式發光元件都具有較高之發光亮度與電流效率。

關鍵字

有機發光二極體；串聯式；電荷產生層； P型摻雜； N型摻雜

並列摘要

This study uses the green fluorescence in organic light emitting devices, and it uses the Alq3 fluorescence as the main light emitting material. The structure is ITO/TAPC(30nm)/Alq3 (60nm)/LiF(0.7nm)/Al(150nm), at the current density of 50 mA/m2, the drive voltage of 8.2 volts, and the current efficiency of 2.95 cd/A. Then, this study uses this structure to become the tandem OLED directly, and this structure is ITO/EL/EL/LiF(0.7nm)/Al(150nm). Because devices which are directly stacked can make the inside impedance to be larger, and let electronics and holes not easily to enter devices, this study can find that the current density is at 50 mA/m2, and the driving voltage is 17.3 volts, but the current efficiency is 1.24 cd/A. To enhance the effect of the current injection, this study adds a charge generation layer (CGL, charge generation layer) between the two EL. In the beginning, this study mixes the P-type material (MoO3) and TAPC together to change the doping ratio and thickness. This structure is ITO/EL/TAPC:MoO3(10nm、30%)/EL/LiF(0.7nm)/Al(150nm), at the current density of 50 mA/m2, the driving voltage of 15.2 volts, and the current efficiency of 3.22 cd/A. The reason of Using MoO3 is that this material can produce holes itself to increase the ability of the current injection and increase the current efficiency. Second, this study adds the N-type material (C60) inside. It can balance electronics and holes in devices, and adjust the thickness of the charge generating layer. The structure mentioned above is ITO/EL/C60 (10nm)/MoO3(4nm)/TAPC:MoO3(10nm、30%)/EL/LiF(0.7nm)/Al(150nm), at the current density of 50 mA/m2, the driving voltage of 16.1 volts, and the current efficiency of 3.53 cd/A. In the end, this study uses LiF(0.5nm)/C60(10nm)/MoO3(4nm)/TAPC:MoO3(10nm、30%) to be CGL, at the current density of 50 mA/m2 , the driving voltage of 16.7 volts, and the current efficiency of 4.23 cd/A. Comparing with the single OLED, the effect of the tandem OLED can enhance 1.43 times. In addition, the luminance and the current efficiency of the tandem OLED are both higher at the same current density.