PPV複合材料發光二極體之特性研究

Abstract

本研究利用有機鹼來合成PPV前驅物，避免傳統使用無機鹼合成PPV造 成無機離子的殘留，能夠有效地增加PPV發光效率。當PPV前驅物與不同量 PVA溶液合成PPV-PVA複合膜時，以PPV-PVA-4(66.4wt/33.6wt)的比例所得 的PPV複合膜，在元件操作電壓下有相對較高的發光效率及較低電流值， 因PPV和PVA之間反應形成單鍵打斷共鍵造成許多區段的共軛鍵帶，當電子 和電洞傳導時易束縛在各區段共軛帶中使電子和電洞結合機率增加，而提 升發光效率。在相同重量百分比的PPV-PVA-4、PPV-PVA/3-APS及PPV/3- APS三個複合膜元件性質比較中以PPV-PVA-4複合膜有相對較高的發光效率 ，且有較大能力減短共軛鍵長度。在相同重量百分比的PPV-PVA-4和PPV/ PEO複合膜比中，PPV-PVA-4複合膜發光效率遠大於PPV/PEO複合膜，表示 適當共軛鍵長度是增加PPV發光效率的主要因素。在不同溫度和時間製程 PPV-PVA-4複合膜時，以160oC,10小時處理的PPV複合膜在操作電壓下有最 高發光效率及在真空下電壓5.5V操作時，在90小時後仍有53%亮度且其EL 光譜和原先EL光譜相同，表示PPV-PVA-4複合膜在此此操作電壓下非常穩 定。 在PPV前驅物階段若用電場來定向極PPV化前驅物再加熱轉化成 PPV，所得PPV複合膜發光二極體都有較高的發光效率。而極化電場的高低 及極化處理的溫度也會影響發光二極體的發光特性 This study focuses on improving the electroluminescent efficiency of the PPV-based polymer LEDs. An organic base was used to synthesize PPV precursor in order to avoid the remain of inorganic ions in the traditional way. The electro-luminescent efficiency of the PPV-based LEDs do increase. When the PPV compositeswere made from the PPV precursor and PVA solution with different composition, the LED of the PPV-PVA (66.4wt/33.6wt) composite materials showed a relativelyhigher efficiency and a lower current. This is due to the reaction between PPV and PVA forming ether linkage (C-O-C) and the conjugation of the systembeing broken. The combination of electrons and holes in PPV. system more easierrelease the energy. At the same weight percentage of the PPV in PPV-PVA-4, PPV-PVA/3-APS and PPV/3-APS. The PPV-PVA-4 LED shows the best electroluminescent efficiency and the shortest conjugated band length. By comparing the LEDs made of PPV-PVA-4 and PPV/PEO, it indirectly proved that PVA formed a chemical bond with PPV and cased the electroluminscenct efficiency promoted. The charac-teristics of PPV-PVA-4 LEDs depend on the processing condition. After heating at 160oC for 10hrs. the PPV-PVA-4 shows a good EL characteristics and a good reliability. The EL characteristics are also improved by polarizing PPV precur-sor at low temperature. The electric field and temperature influence the charac-teristics of light emitting diodes.