高分子發光二極體(PLED)是共軛高分子近年來最具有工業發展潛力之應用之一。與小分子發光二極體比較具有製程簡單、低成本、可大面積化、可做曲饒性面板、輕薄化等優點。但目前遇到了操作壽命短、操作電壓高、量子效率低、電極介面接合較差等問題。本研究探討利用鋰鹽(LiClO4)與高分子固態電解質(PEO)混摻入發光材料MEHPPV之方法，發現可以有效降低PLED工作電壓。鋰鹽經由電解質柔軟鏈鍛順利進入MEHPPV，並且效能比未添加高分子固態電解質(僅添加鋰鹽或純MEHPPV)之樣品具有較低之操作電壓，較高極子數目，而亮度也相當。 本文經由7Li NMR觀察混摻樣品之離子運動性，並了解鋰離子之分布狀況。研究發現MEHPPV/(PEO+Li) =60/40相容性最好有較多的鋰離子進入發光材料主結構因其具有較低活化能，在結構上鋰鹽有效的經由PEO的鏈鍛doping進入MEHPPV並且doping於陰電性較高之烷氧基與苯環之間，生成極子(polaron)與雙極子(bipolaron)，因此降低能帶差，並增加共軛長度，使得操作電壓因此降低了將近2V。導電度相較於未添加PEO者，增加了101~105，並且因為共軛長度經由PEO的添加而增長，UV及PL發現了光譜往紅位移方向移動將近10nm。在放光效率中以MEHPPV/(PEO+Li)=50/50具有最高螢光強度者具有最佳螢光效率，高於50%MEHPPV之樣品因PEO鏈段的捲繞反而降低了螢光性質。 本研究對於鋰離子的配位，運動性，活化能及表面紋理對於光性元件之關聯性作探討，希望對將來高分子發光二極體之改質有個參考依據。 Polymer light-emitting diode (PLED), entails problems such as short lift time, low quantum yield, high running voltage and insufficient interface adhesion between electrode and light emitting materials. In current study we explore a tunable doping by composite a polymer electrolyte, with the light emitting materials, MEHPPV. The study showed that the flexible PEO’s chain motion facilitated the ion doping with MEHPPV, which are otherwise immiscible with ion salt. As a result of the modification, it enhances electron and hole recombination, lowered the work potential and improved the quantum efficiency. The dynamics and local structures of lithium ion in the electrolyte composite PLED polymer composite is well illustrated by 7Li NMR. The best miscibility is achieved with MEHPPV/(PEO+Li)=60/40 wt% with the highest amount of lithium doped in MEHPPV. The doping forms polaron and bipolaron and decreased energy band gap, and successively lowered the work potential of about 2V with the conductivity increases 101~105 fold. UV and PL spectra indicated increasing conjugated length resulting form the more effective doping. Surface analyses from AFM and activation energy (Ea) measured from NMR line width provided detailed understanding of the coordination structures and exchange of lithium between MEHPPV and PEO, which contributes to the optical properties. The approach serves as a guidance to improve PLED optical and physical properties with tunable doing by polymer electrolytes.
