含芴衍生物與聚合物之合成及其在溶劑製成白色螢光與磷光有機發光二極體之應用

Abstract

本研究主要分成三部分，探討以溶劑製程(solution process)來製作白色螢光與磷光的有機發光二極體元件。本研究第一部份，係利用一種新的方法(azide-alkyne click reaction)來合成出高分子量的單一高分子鏈白光聚芴聚合物，首先合成四個含有特殊末端官能基的基礎聚合物PFs(PFB2, PFB1, PFG1和PFR1)，其皆有非常高的熱穩定性(Tg＞100 ℃)，其中，PFB1, PFG1及PFB1分別發藍、綠和紅光，PFB2是在末端有N3基團發藍光的聚合物，PFB2在100 ℃時能夠在高極性溶劑(如：DMF/toluene共溶劑)中，不需要金屬催化劑的反應條件下，很快速地跟含有末端acetylene基團的聚合物PFB1, PFG1及 PFR1進行反應產生triazole五元環。將四個基礎聚合物以特定的比例進行click reaction，可以生成triazole五元環的架橋將PFs連接起來，進而得到高分子量的白光聚合物WPFs(WPF1~6)，並成功將其應用在高分子有機發光二極體元件，其中，以WPF5當作發光材料可以得到一最大亮度7551 cd/m2和最大效率5.5 cd/A且CIE座標在(0.30, 0.33)的白光元件。 本論文的第二部份，係以芴為基礎，合成出含carbazole和phenylsilane基團的主發光體材料(FCzSi)，並將其應用在溶劑製程的藍光磷光有機發光二極體(PhOLED)。此新穎的主發光體材料除了擁有很好的熱穩定性(Td=366.8 ℃, Tg=103.5 ℃)。另由於其在carbazole的3,6-位置接了四個剛硬、立體障礙大的triphenylsilane基團，讓分子的共軛長度被有效地限制住，因而使得FCzSi展現出非常高的三重態能階(ET=2.72 eV)。FCzSi在薄膜態的PL螢光光譜中也表現出非常穩定的光色穩定度，這是因為sp3混成的triphenylsilane基團破壞了分子結構的平面性使得分子變得更立體，也就降低了分子堆疊和激子(excimer)產生的機會。以FCzSi為主發光體材料；FIrpic、Ir(mppy)3、Ir(btp)2(acac)為磷光客發光體，成功地以溶劑製程製作了藍光及白光的元件，其中，device B3的CIE座標為(0.17, 0.34)，最大亮度與效率分別為3450 cd/m2與6.69 cd/A；device W12為CIE座標(0.35, 0.37)的白光磷光元件，最大亮度與效率分別為3198 cd/m2與6.23 cd/A。 本研究第三部分，係合成含oxetane基團的紅光銥錯合物(Ir-R)和聚芴高分子(PF-Cbz)，利用其可光聚的性質，發展多層PLED元件。Ir-R為一最大放射波在616 nm的紅色磷光材料，PF-Cbz除了熱穩定性佳(Td為404 ℃，Tg為120 ℃)，且其三重態能階為2.52 eV，非常適合當Ir-R的主發光體材料。以PF-Cbz作主發光體、Ir-R作客發光體和TPBi作電子傳輸材料，用溶劑製程製作多層PLED元件，用以提升元件的效率。

The goal of this study is aimed to fabricate white fluorescent and phosphorescent light emitting diode devices by solution process. In the first part, we reported a new way to synthesize single-chain white light-emitting polyfluorenes (WPFs) with an increased molecular weight using azide-alkyne click reaction. Four basic polymers i.e. PFR1, PFG1, PFB1 and PFB2 with specific end-capping were synthesized and used to prepare the WPFs, PFR1 emits red light, PFG1 emits green light, while PFB1 and PFB2 emit blue light. All the polymers exhibited high glass transition temperatures (Tg >100 °C) and excellent thermal stability. The blue-light polymer (PFB2) end-capped with azide groups was reacted with acetylene end-capped polymers, PFB1, PFG1 and PFR1 to form triazole-ring linkages in polar solvents such as DMF/toluene co-solvent at moderate temperature of 100 °C. No metal-catalyst is needed in this click reaction. Several WPFs which consisted of these four basic polymers in certain ratios were derived, and the PLED device based on the high-molecular-weight WPF was achieved and demonstrated a maximum brightness of 7551 cd/m2 (at 12.5V) and a maximum yield of 5.5 cd/A with CIE coordinates of (0.30, 0.33) using fine-tuned WPF5 as emitting material. In the second part of this study, a novel fluorene-based host material (FCzSi) which containing carbazole and phenylsilane groups, is synthesized and utilized for solution processed blue phosphorescent organic light-emitting diodes (PhOLEDs). This new host material exhibited a excellent thermal stability of Td = 366.8 ℃ and Tg = 103.5 ℃. The 3,6-disubstitued rigid and bulky phenylsilane groups on the carbazole units confined the conjugation length of FCzSi effectively. This is the reason why the host material shows a fairly high triplet energy (ET = 2.72 eV). FCzSi also exhibited good color stability in photoluminescence film state. The incorporation of four sp3-phenylsilane groups destroyed the structure planarity of FCzSi and decreased the opportunity of aggregation and excimer forming in PL film. Solution processed blue and white electrophosphorescent devices were achieved by doping common-used FIrpic, Ir(mppy)3 and Ir(btp)2(acac) into our host FCzSi in various concentrations. Device B3 showed a maximum brightness of 3450 cd/m2 (at 12.5V) and the maximum yield of 6.69 cd/A with CIE coordinates of (0.17, 0.34) while 15 % FIrpic was doped with FCzSi. Device W12 emitted a white light with CIE coordination of (0.35, 0.37), maximum brightness of 3198 cd/m2 and maximum yield of 6.23 cd/A. In the third part of this study, oxetane containing iridium complex and polyfluorenes were synthesized. Solution process multilayer PLED device was developed due to the photo-crosslinking property of oxetane groups. Ir-R is a red phosphor that exhibits phosphorescent emission at 616 nm. PF-Cbz shows good thermal stability with Td at 404 ℃and Tg at 120 ℃. Moreover, PF-Cbz possesses a fairly high triplet energy (ET=2.52 eV). Solution process multilayer PLED device improved the device efficiency well by using Ir-R as a dopant, PF-Cbz as a host and TPBi as a electron transporting material.