多層結構共軛有機高分子發光二極體之研究與應用

Abstract

本論文研究多層元件結構設計對於有機高分子發光二極體的元件表現的影響。研究重點在於探討影響高分子發光二極體發光效率的因素。在本研究裡，我們發現元件中的電子與電洞平衡是影響元件效率的主因。尤其以高分子材料而言大多是有利於電洞傳輸，故要達到高效率的目的在於提升元件中的電子電流。我們欲利用多層元件結構來達成元件中電子電洞平衡的目的。故本研究之主要重點之一為發展多層溶液塗膜方法，避免在濕式製程中各有機層製作時的互溶問題，以達成利用溶液製作多層結構元件的目的。本研究成功發展出兩種塗膜方法皆可達成多層結構之目的，一為利用緩衝層溶液保護原先已形成之有機高分子薄膜；另一為利用刮刀塗膜法加上加熱器，此法在於加速溶劑揮發速度，以免造成溶劑向下破壞原先之有機高分子薄膜。利用此二法我們已成功製作出多種高效率多層元件。除了元件結構之外，本研究並探討分子量對元件效率的影響，發現高分子量的材料其電子傳導性較佳，可達高效率的目標。另外在發光層中摻雜三重態發光體並結合多層元件結構設計，製作高效率有機發光二極體亦有探討。

In this study we want to achieve high-efficiency polymer light-emitting diodes (PLED) by proper multilayer device structure design. We found the main factor to decide the efficiency would be the electron-hole balance, especially the electron currents in devices. The electron-hole balance can be achieved by multilayer structure. However the multilayer structure is difficult to achieve by solution process due to the fact that the mutual dissolution problem between layers. We have developed two ways to overcome the dissolution problem and to achieve multilayer structure. One is the liquid buffer layer method, which uses 1,2-propylene glycol to prevent the polymer thin films from dissolving by the next solution; the other is the blade coating with high speed and a heater, which accelerates the speed of the solvent evaporation. Several high-efficiency multilayer PLEDs have been achieved by these two ways. In addition to device structure, we have studied the relation between molecular weight and the efficiency. We found that the high molecular weight would cause high electron current density as well as the high efficiency. Finally, high-efficiency PLEDs have been achieved by blending triplet emitters into the polymer host, combining the multilayer structure design.