- 學位論文
有機薄膜電晶體全溶液製程開發與介面特性之研究
Interfacial Properties Study and Development of All-Solution-Processing Organic Thin Film Transistors
摘要
在分子電子元件領域中，包括：有機場效電晶體領域，導電高分子聚合物poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)經常被作為軟性電極(soft electrode)的材料。本論文我們將以全溶液製程(all solution process)來製作以PEDOT:PSS為電極之有機薄膜電晶體元件並深入探討有機半導體分子triethylsilylethynyl anthradithiophene (TESADT)與導電高分子聚合物間介面之特性。於此，我們感興趣之議題包括TESADT/PEDOT:PSS介面間分子能階狀態、分子排列位向及成長形貌。我們所採用的表面分析技術包含紫外光光電子能譜、X光光電子能譜、近緣X光吸收細微結構光譜及原子力顯微鏡。 在實際製作之有機薄膜電晶體元件效能方面，底接觸式的元件，其電洞遷移率為0.053 cm2/Vs，門檻電壓為6.4 V，開關電流比為8.3 × 105，而頂接觸式的元件，其電洞遷移率為0.035 cm2/Vs，門檻電壓為1.6 V，開關電流比為2.2 × 105。此電性結果與以Au為電極之電晶體元件相比較，以G-PEDOT:PSS為電極之元件其電洞遷移率普遍優於以Au為電極之元件，主要原因為TESADT會進入G-PEDOT:PSS之寬鬆結構內，形成一厚度約10 nm的混雜區域，且TESADT會靠近PSS鏈，PSS為電洞施者，而TESADT為電洞接受者，電洞摻雜使得電洞注射能障減小，約0.48 eV，元件具有較佳的電洞注射效率。而受汙染之Au/TESADT介面的電洞注射能障為0.88 eV，元件之電洞注射效率較差。
關鍵字
有機薄膜電晶體並列摘要
Conducting polymer of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) is frequently used as soft electrode materials in molecular electronics including organic field effect transistor (OFET). In this thesis, we will report on the fabrication of all-solution-processed organic thin film transistors consisted of PEDOT:PSS polymer and a semiconducting material of triethylsilylethynyl anthradithiophene (TESADT). All the relevant interfacial properties between polymer electrodes and TESADT will also be investigated. The issues of particular interest are energy level alignment, thin film morphology and the molecular alignment of TESADT molecules on PEDOT:PSS substrate. The techniques in use include Ultraviolet Photoelectron Spectroscopy (UPS), X-ray Photoelectron Spectroscopy (XPS), Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy and Atomic Force Microscope (AFM). The bottom-contact OFET devices were fabricated, and the average OFET mobility reaches 0.053 cm2V-1S-1, with a threshold voltage at 6.4 V and an on/ off current ratio of 8.3 × 105. The top-contact OFET devices were also fabricated, and the average OFET mobility achieved is 0.035 cm2V-1S-1, with a threshold voltage at 1.6 V and an on/ off current ratio of 2.2 × 105. Comparing these results with the device performances of OFET consisted of Au electrodes, the bottom contact PEDOT:PSS based devices have better performance than Au based devices. A smaller hole injection barrier of 0.48 eV and a better injection efficiency were found for the TESADT/PEDOT:PSS interface which belong to an ohmic contact resulting from the diffusion of TESADT molecules into the structure of PEDOT:PSS. However, a higher hole injection barrier of 0.88 eV and a worse injection efficiency were found for the TESADT/Au interface which belong to a Schottky contact.