以緩衝層提升可撓式有機發光二極體發光效率之研究

本研究使用PEDOT:PSS、Teflon、TPD in CHCl3與α-NPD in CHCl3作為可撓式有機光二極體之陽極緩衝層，除Teflon之外，皆使用旋轉塗佈的製程方式將緩衝層沈積於ITO基板上，目的在於降低ITO表面之粗糙度並改善有機材料之附著性，以提升可撓式有機光二極體之發光效率與可撓曲性。在以PEDOT:PSS作為緩衝層之研究中，元件結構為：ITO/PEDOT:PSS/NPB (40 nm)/Alq3 (60 nm) /LiF/Al，研究結果顯示，當PEDOT:PSS厚度為20 nm時，與無緩衝層之元件相比，最大發光效率可由2.0 cd/A提升至3.75 cd/A。若將PEDOT:PSS厚度增至80 nm時，元件發光效率可再提升至4.75 cd/A，最大亮度為1600 cd/m^2 @ 10 V。之後若再將Alq3厚度增加為100 nm並於PEDOT:PSS上蒸鍍1 nm之Teflon，由於激子放光效率增加，因此元件最大亮度可提升至2040 cd/m^2 @ 10 V，最大發光效率可穩定維持 ≧ 6.0 cd/A @ 1.0 ~ 27.4 mA/cm^2。而在以TPD in CHCl3作為緩衝層之研究中，元件結構為：ITO/TPD in CHCl3/NPB/Alq3/LiF/Al，研究結果顯示，當TPD in CHCl3、NPB、Alq3厚度分別為35、20、80 nm時，元件之發光效率提升至4 cd/A 以上、亮度為2000 cd/m^2 @ 8.5V。若以α-NPD in CHCl3取代TPD in CHCl3作為緩衝層，當α-NPD in CHCl3厚度為55 nm，NPB與Alq3厚度為20、80 nm時，元件亮度為1220 cd/m^2 @ 7.5 V，發光效率可穩定維持在5.0 cd/A。若於α-NPD in CHCl3上再蒸鍍1 nm之Teflon，NPB與Alq3厚度不變，則元件發光效率可提升至6.5 cd/A，最大亮度為1200 cd/m^2。

關鍵字

non

並列摘要

In order to improve the luminance efficiency and flexibility of the flexible organic light-emitting diodes (FOLEDs), four kinds of buffer layer were inserted between ITO and hole transport layer in the device of ITO/buffer/NPB (40 nm)/Alq3 (60 nm)/LiF/Al. The buffer layer employed is PEDOT:PSS, PEDOT:PSS/Teflon, TPD or α-NPD . The TPD and α-NPD were first solved in chloroform (CHCl3) before spin-coating. Firstly, when 20 nm PEDOT:PSS was employed as buffer layer, the FOLED luminance efficiency increased from 2 to 3.75 cd/A in comparison with the original device without any buffer layer. If PEDOT:PSS thickness increases from 20 to 80 nm, the luminance efficiency increased to be about 4.75 cd/A and the maximum luminance was 1600 cd/m^2 @ 10V. Next, 1 nm Teflon was further coated on the PEDOT:PSS surface, i.e. PEDOT:PSS/Teflon as the buffer layer. The effects of PEDOT:PSS thickness in the PEDOT:PSS/Teflon buffer layers on the FOLEDs were also studied. Finally, when the Alq3 thickness was increased from 60 to 100 nm in the FOLEDs using PEDOT:PSS/Teflon as the buffer layers, the maximum luminance and efficiency were increased to as high as 2040 cd/m^2 and 6.1 cd/A, respectively. Next, the effects of TPD in CHCl3 as buffer layer were studied. The spin-coated TPD in CHCl3 film has better adhesion to both ITO and NPB material, which can improve the luminance efficiency of flexible OLED. When 35 nm TPD in CHCl3 was employed as buffer layer, the thickness of NPB and Alq3 with 20 and 80 nm. The maximum luminance and efficiency can be increased to as high as 2000 cd/m^2 and 4.0 cd/A, respectively. Finally, we used α-NPD in CHCl3 to replace TPD in CHCl3 as buffer layer and the thickness fixed at 55 nm. The luminance efficiency increased to be about 5.0 cd/A and the maximum luminance was 1220 cd/m^2 @ 25 mA/cm^2. If 1 nm Teflon was further coated on the α-NPD in CHCl3 surface, the maximum luminance efficiency can be increased to as high as 6.5 cd/A and the maximum luminance was 1200 cd/m^2.