取代基效應對於有機發光材料之理論探討

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Title:	取代基效應對於有機發光材料之理論探討
Other Titles:	Theoretical investigation of the substituent effect for organic light emitting materials
Authors:	戴欽坤;Tai, Chin-kuen
Contributors:	淡江大學化學學系博士班王伯昌;Wang, Bo-cheng
Keywords:	取代基效應;吸收放射波長;分子軌域躍遷模式;密度泛含理論;Maleimide;Alq3;substituent effect;maximum absorption wavelength;emission wavelength;HOMO and LUMO energy;DFT-B3LYP;TD-DFT;PCM
Date:	2008
Issue Date:	2010-01-11 02:49:08 (UTC+8)
Abstract:	近年來有機發光二極體受到許多研究人員注目與投入心血發展，然而現今的有機發光材料有一些必須要克服必須要克服的地方，例如有機發光二極體的元件壽命及發光強度等等。另外，有機發光二極體構成彩色所基本需要的三原色紅色、綠色，藍色之發光色彩純度，也遇到瓶頸。使用取代基與發光分子鍵結是一般常見的化學修飾策略，故本篇論文即著重在取代基在有機發光分子中，所扮演的角色並討論取代基對分子性質的影響。本論文的第一部份是針對maleimide分子，研究取代基對分子本體的結構變化以及吸收-放射波長和分子軌域躍遷行為。取代基會導致分子結構發生變化，使得maleimide衍生物產生出相當明顯的stokes shift現象。其中在maleimide分子的3、4位置使用取代基取代時，取代基將會造成最明顯的stokes shift現象。透過PCM模型的導入，也說明不同極性的溶劑環境下，分子吸收與放射波長受到的影響。本論文的第二部份則是針對Alq3分子，研究不同推拉電子特性的取代基與延伸π電子共軛長度對整體分子的分子軌域能量和吸收波長的影響。拉電子取代基會對顯著影響整體分子的HOMO分子軌域能量。推電子基會對整體分子的HOMO、LUMO分子軌域能量造成明顯的影響。不同鍵結位置的取代基也會使得衍生物的吸收波長產生的紅位移。延伸π電子共軛長度，將會導致取代基對整體分子的分子軌域能量有更大能量變化。 The molecular structure properties, the optical properties, and the molecular orbital transition of the organic light-emitting materials were calculated by using the density-functional theory (DFT), CIS and the time-dependent density-functional theory (TD-DFT) methods. In the part I, for N-substituted maleimides, the substituent gives only a slight influence on the maleimide chromophone. For 3,4-substituted maleimide, the steric repulsion between substituent and maleimide chromophone influences the extent of π-delocalization and the molecular conformation. The calculated maximum absorption wavelength and emission wavelength of maleimide derivatives are in good agreement with the experimental data. In the gas phase, both absorption and emission peaks are red-shift as compared to the non-substituted maleimide. For the 3,4-substituted maleimdies, the effect of substitution produces the most significant spectral red-shift as compared to other maleimdies. In the part Ⅱ, for Alq3 derivatives, the election-donation groups influence the HOMO energy significantly, and the election-withdrawing groups influence both the HOMO and LUMO energy. The maximum absorption wavelength of Alq3 derivatives are red-shift by substituents which connect at different bonding site. The significant molecular orbital energy difference can be produced by extent of the π-conjugation length between substituent and Alq3 chromophone.
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