論多元并苯雜環共軛分子之側鏈及末端取代基對固態結構和有機場效電晶體元件表現的影響

Abstract

本研究著重於探討雜環并苯的共軛分子體系中，側鏈取代基及末端基團對共軛分子之固態結構堆積及其元件效率於有機場效電晶體(Organic field-effect transistor, OFET)中的影響。共軛分子材料由國立臺灣大學汪根欉老師實驗室提供，共有8種樣品，利用這些共軛核心相同但有一處官能基改變的分子，觀察側鏈烷基長度改變、末端基團不同、加入End-capping基團及缺電子End-capping基團所造成的變化。本研究主要利用本實驗室研發之PDMS輔助長晶法(PDMS-Assisted Crystallization, PAC)生成晶體陣列，並將其作成OFET，以元件量測真空腔體及電流電性分析系統量測其元件效能，結果以加入End-capping基團具有最顯著的改善效果，樣品DP-EH-HA2具有最好的元件表現，為4.67x10-2 cm2V-1s-1。為了研究共軛分子之固態結構，本研究利用國家同步輻射研究中心之掠角X光繞射技術(Grazing incidence X-ray diffraction, GIXRD)取得各分子out-of-plane及in-plane之晶格參數(lattice parameter)，藉此觀察分子在基板上的固態結構排列有序程度。本研究希望透過分析共軛分子之排列，進而了解其固態結構對有機場效電晶體之元件效能的影響。亦可藉由研究這些不同的雜環并苯共軛之衍生物，來幫助化學家了解如何設計共軛分子才可以達到更高的元件效率。

Solid-state structures of conjugated molecules play an important role in the field-effect transistor (FET) performances of the molecules. Multi-fused heteroacenes (HA) are useful building blocks for molecules used in optoelectronic devices. Although the influences of the constituent aromatic units on the chemical properties of HAs have been known, their influences on the physical structures of the HA derivatives have not been systematically studied. Here, a series of 8 heteroacene (HA) derivatives provided by Professor Ken-Tsung Wong’s laboratory at National Taiwan University were studied. The molecules were divided into three groups based on the chemical structures of their HA cores (HA1: 4,9-Bis(2-ethylhexyl)-thieno[3,2-b]thieno[2''',3''':4'',5'']pyrrolo[2'',3'':4',5']thieno[2',3':4,5]-thieno[2,3-d]pyrrole, HA2: 6,12-Bis(2-ethylhexyl)-Indolo[2'',3'':4',5']thieno[2',3':4,5]thieno[3,2-b]indole, HA3: 4,5-Bis(2-ethylhexyl)-dithieno[2,3-d:2',3'-d']thieno[3,2-b:4,5-b']dipyrrole). Crystal arrays of the HA derivatives were prepared by the PDMS-assisted crystallization (PAC) procedure. By analyzing the polarized optical microscopy (POM) images, grazing incidence X-ray diffraction (GIXRD) patterns, and OFET performances of the HA derivatives, it was found that the lateral alkyl substituents and the end-capping groups can significantly affect the solid-state morphology and the OFET performances of the molecules.