以化學氣相沉積聚合法製備共軛高分子和無機/有機複合材料及其光電性質之研究

The Optoelectronic Properties of Conjugated Polymers and Inorganic/ Organic Hybrid Materials Prepared with Chemical Vapor Deposition Polymerization Processes

蕭章道(Chang-Tao Hsiao)

指導教授 ： 呂世源

國立清華大學/工學院/化學工程學系/博士(2009年)

https://doi.org/10.6843/NTHU.2009.00773

摘要

中文摘要
共軛高分子因其獨特的光電性質，所以在過去幾十年來一直被廣泛的研究。其應用範圍除了我門所熟知的光致發光元件及顯示器技術外，在顯示器背光源、一般照明、光伏元件方面也持續被探討與研究。
本研究嘗試以氣相法製備共軛高分子、無機/有機混合系統及熱解碳材(pyrolytic carbon)，除進行材料分析及成膜形態(morphology)之觀察，最重要的是其與光電性質的關聯性，以期能在瞭解其物性、化性與光電性質後，將此材料運用於共軛高分子光電元件上。本研究共分為三大主題：
(一) 以化學氣相沉積聚合(CVDP)法製備共軛高分子薄膜：：我們以SPR法合成液相前驅物聚電解質(Poly(xylylene tetrahydrothiophenium chloride, PXT)溶液，並以核磁共震質譜儀(NMR)及霍式轉換紅外線光譜儀 (FTIR)分析其中間物及產物的組成；此液相前驅物可採用旋轉塗佈法塗佈於基材上經熱轉換後得到PPV薄膜。此外，我們也以化學氣相沉積聚合法(chemical vapor phase deposition polymerization, CVDP)法製備PPV薄膜，並比較二者間光電性質之差異。發現以化學氣相沉積法製備的薄膜其量子產率(quantum yield)較低，此現象可能與膜的緻密度所引發的發光中心濃度淬熄(concentration quench)有關。另外我們也成功的以CVDP法製備出共軛高分子PPP，並以簡單的基材表面親疏水性處理來控製高分子鏈堆疊(chain conformation)與成膜形態(film morphology)，進而控制其光電行為。
(二) 以化學氣相沉積聚合(CVDP)法製備有機/無機混合系統：我們以CVDP法成功製備出Zn/PPV金屬/高分子錯合物，除了證實氣相法也能進行化學修飾將金屬原子接於主鏈上，也大幅改善了量子產率近七十倍。此外我們以共進料(co-fed)CVDP法製備出有機/無機半導體奈米複合膜PPV-CdS及PPV-ZnS，藉由掺雜物(inclusion)本身的物性及成膜形態控制(morphology control)，可以操控複合膜之光電性質。
(三) 以化學氣相沉積(CVD)法製備熱解碳(pyrolytic carbon)膜及於DSSC上之應用：本實驗以CVD法將熱解碳直接沉積於石英基材上而製備出小孔隙(micropore)、親水性、金屬光澤、鏡面反射、具觸媒活性及導電性的碳膜，而直接應用在DSSC的對電極上。我們比較材料的比表面積、孔徑分佈、片電阻及晶相，發現觸媒活性為主要影響光轉換效率的主因，以循環伏安法及電化學阻抗分析更確認觸媒活性之重要性。雖然熱解碳經熱處理而提升了光轉換效率，但與 Pt對電極仍有差距。雖然熱解碳光轉換效率不如Pt，但改善空間很大，因此頗具開發潛力。
由研究結果顯示，發光波長、發光強度及效率受到共軛高分子分子鏈堆疊(chain conformation)與成膜形態(film morphology)、摻雜物種類、尺寸及形態的影響；在對電極的研究上，材質的觸媒活性為影響效率的主因，因此具有導電性、觸媒活性且價格便宜的熱解碳相當具有開發潛力，將對DSSC的應用有很大的助益。

關鍵字

化學氣相沉積聚合法 ； 共軛高分子 ； 無機/有機複合材料 ； 有機發光元件 ； 太陽能電池

並列摘要

Abstract
In the past several decades, conjugated polymers have been extensively and intensively investigated because of their unique electroluminescent properties. The most well known application of these materials is the organic light emitting diodes. It is not only used in display technology, but also applied in lighting, such as backlight module of TFT-LCD, general light source, and organic solar cells.
In this thesis, we investigated the gas route preparation and optoelectronic properties of PPV, inorganic/organic hybrid system, and pyrolytic carbon. The relationship between the structure and optoelectronic properties has been investigated. The three main topics of this research are:
1) Conjugated polymer thin film preparation with CVDP (chemical vapor phase deposition polymerization) methods︰The SPR method was employed to synthesize PXT to be a precursor of a liquid phase route. Both FTIR and NMR spectra were obtained to identify the composition of the intermediate and final product in the reaction. The precursor, PXT, was cast on the substrate via spin coating, and formed PPV films after thermal convertion. Besides, we used a CVDP method to prepare PPV films and compared the PL quantum yields with those from the PPV films prepared by spin coating. The results showed that the PPV films prepared by the CVD method exhibited lower PL quantum yields. It may be caused by the dense structure of the CVD films, leading to concentration quench of the luminescent centers. We also used the same method to prepare poly(p-phenylene) films in one-step successfully. The polymer chain conformation of the film can be effectively adjusted through a simple surface treatment of the substrate. The variations in film morphology induced by the substrate characteristics led to significant changes in the optoelectronic properties of the film.
2) Organic/ Inorganic hybrid system preparation with CVDP method: The highly photoluminescent Zn/PPV complex films were successfully prepared with a direct complexing of Zn to PPV in a facile CVDP process for the first time. A two order of magnitude improvement in PL quantum yield was achieved through this metal complexing. The present approach can be readily extended to other photoluminescent metal-polymer systems. Besides, a novel co-fed chemical vapor deposition polymerization process was developed to successfully fabricate PPV-CdS and PPV-ZnS nanohybrids. The morphology of the nanohybrids can be effectively tuned through a simple control of the relative precursor concentration in the deposition system. Markedly different nanohybrid morphologies, ranging from well dispersed nanocrystals to continuous bulk heterostructures, were realized. The variations in morphology corresponded to according variations in optoelectronic properties attributable to the the p-n interfaces formation.
3) A pyrolytic carbon thin layer deposited on quartz substrate serving as a counter electrode for dye-sensitized solar cells: The chemical vapor deposition (CVD) pyrolytic carbon thin layer deposited on quartz substrates from biphenyl ring precursor monomer 4,4'-bis-chloromethyl-1,1'-biphenyl and served as a CE for DSSC applications was investigated. The material possesses metal-like, hydrophilic, microporous, conductive, and catalytic properties. We demonstrated that the catalytic properties with the CV and EIS methods. Although the catalytic activity was less than that of the traditional Pt counter electrode, the pyrolytic carbon material has a room for improvement and may potentially replace the noble metal electrode in DSSC applications.
From the present study, the conjugated polymer’s chain conformation, film morphology, dimension, and dopant were found to affect the luminescence position, strength, and efficiency. As for the new carbon material for the DSSC applications, the catalytic activities dominate the conversion efficiency.

並列關鍵字

CVDP ； Conjugated Polymer ； Inorganic/ Organic Hybrid Materials ； OLED ； Solar Cell

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