具奈米結構之二氧化鈦/共軛高分子與氧化鐵/聚丙烯酸複合材料之合成、性質與應用

Nanostructured TiO2/Conjugated Polymer and Fe3O4/PAA Composites: Synthesis, Properties and Photovoltaic Application.

林怡君(Yi-Jun Lin)

指導教授 ： 邱文英

共同指導教授 ： 王立義

國立臺灣大學/工學院/化學工程學研究所/博士(2007年)

https://doi.org/10.6342/NTU.2007.01300

摘要

本研究主要包括三大部分，包含二氧化鈦、氧化鐵奈米材料之合成與探討；以電化學聚合法製備光敏性聚噻吩/二氧化鈦奈米複合材料以及混成太陽能電池元件之製備。內容共分為三個章節。
第一章最主要在於合成具有不同型態之二氧化鈦及氧化鐵奈米材料。在二氧化鈦方面，首先探討利用溶膠-凝膠反應法合成多孔性二氧化鈦薄膜之性質，並進一步合成具有高穩定性及單一粒徑分佈之二氧化鈦粒子，此部分探討有機溶劑中水含量、前驅物濃度以及溶劑種類對於粒子之型態及粒徑分佈之影響。經由實驗參數之控制，我們可得到高穩定性及單一粒徑分佈之二氧化鈦粒子，且可調控粒徑分佈在50 nm 到252 nm 範圍之間。另外，我們也利用evaporation-induced
self-assembly (EISA)方式，藉由溶劑之揮發，造成模版試劑和無機物種之間的自組裝，形成規則性介孔結構，製備具有序連續結構之網狀奈米TiO2 無機薄膜材料。氧化鐵方面，首先以化學共沈法合成Fe3O4粒子，並利用高分子poly(acrylic acid)穩定分散Fe3O4 微粒，形成具有高穩定之磁性流體，進一步探討磁性流體之性質。另外，利用熱裂解法合成大小均一之Fe3O4 磁性粒子，可將Fe3O4 磁性粒子之粒徑控制在5 nm 到15 nm 之間。本章中，我們也利用水熱法處理二氧化鈦以及氧化鐵奈米粒子，以製備奈米管及奈米線。製備所得之二氧化鈦奈II米管表面積大幅增加，其表面積約為原本奈米粒子之六倍
第二章以電化學聚合法製備光敏性聚噻吩/二氧化鈦奈米複合材料，應用電化學聚合法直接將有機導電高分子材料以in-situ 聚合方式與無機半導體材料直接形成active hybrid layer。本章中，我們將深入探討電化學反應參數、混合溶劑中水的比例、電流密度以及酸濃度對於聚噻吩/二氧化鈦奈米複合材料之附著性、表面型態、以及電化學性質之影響。我們可藉由反應參數的調控，得到表面型態均勻、附著性佳且電化學性質穩定之複合材料。
第三章主要以電化學聚合法製備聚噻吩/二氧化鈦太陽能電池。利用噴霧熱解法製備緻密二氧化鈦層，並導入此緻密層以製備元件。本部分詳細探討製備緻密二氧化鈦層時，實驗參數對於二氧化鈦膜之表面型態以及對於元件效率之影響。實驗結果顯示導入此二氧化鈦緻密層後，元件效率有顯著之提升，效率較未導入此緻密層時提高約一千倍，且Fill factor 由0.2 提高到0.51。本章中會更進一步探討緻密層之層數對於元件之光電特性之影響。

關鍵字

二氧化鈦/共軛高分子複合材料 ； 電化學聚合 ； 氧化鐵/聚丙烯酸複合材料 ； 有機太陽能電池

並列摘要

This thesis divided into three parts. The synthesis of metal oxide materials, including titanium dioxide (TiO2) and iron oxides (Fe3O4) were described in Chapter 1. The experimental procedures and characterization results of successful synthesis of crystalline TiO2, and Fe3O4 with various shapes and morphologies were reported and discussed in this chapter. In the following part of this work, the synthesis and characterization of TiO2 nanocrystals with a rather small particle size distribution were presented. The effects of titanium precursor concentration, solvent, and water content on the morphology and particle size distribution of TiO2 colloids were also briefly discussed. The diameter of these titania spheres can be easily tuned from 50 to 252 nm by varying the precursor concentration from 0.68 mM to 1.94E-2 M. Titania thin film produced by evaporation-induced self-assembly (EISA) route were also studied, which has a highly ordered mesostructure, narrow pore-size distribution, relatively high specific surface area, and very good thermal stability. Moreover, the structure was stable up to 400℃ and contains channel walls with anatase nanocrystallites. Importantly, under modified film aging conditions, optically transparent and crack-free thin films were obtained by the deposition onto a compact TiO2 layer. A part of this chapter presented the methods used to synthesize and characterize the magnetite materials. In the chapter, a series of magnetic materials with different shapes and morphologies were proposed and studied.
In organic/inorganic hybrid photovoltaic cells, the inherent incompatibility of inorganic particle and conjugated polymer frequently causes microscopic separation in the interface of two materials, thus significantly reducing its interfacial photo-induced charge transfer efficiency. In Chapter 2, a series of photoactive hybrids were prepared by the electrochemical polymerization of bithiophene into a nanoporous TiO2-coated ITO glass using chronopotential method in pure acetonitrile solution, or in a water/acetonitrile mixed solvent at different current densities. The growth conditions for the preparation of well defined smooth and adhesive polybithiophene films were demonstrated. Furthermore, the morphologies and electrochemical properties of the as-prepared polybithiophene/TiO2 photoactive hybrid materials were described in this chapter.
In Chapter 3, it describes the details of the preparation of organic solar cells by in-situ electropolymerization method. In photovoltaic cells, the use of an additional blocking TiO2 layer was essential to avoid short circuiting and loss of current through recombination at the FTO electrode. A method of preparation of a compact TiO2 layer by spray pyrolysis technique, and its standardization for the solar cell fabrication was discussed. The nature, structure and morphology of this layer with increasing thickness was examined with scanning electron microscopy (SEM), and the effects of this compact layer on the photovoltaic properties of the corresponding solar cells were also studied by looking into the current(I)-voltage(V) characteristics of a solar cell. Influences of the spraying cycles of this compact layer were also investigated in this chapter. The results indicated that an optimum spraying cycles of compact TiO2 layer was found to be the key issue to give the best results in terms of photovoltaic properties, and the layers of blocking TiO2 film should lie in the optimized region. In our experimental, this corresponds to below 10 spraying cycles in terms of surface morphology and photovoltaic properties. The results of this thesis demonstrate that this study provides a facile and successful route for growing conducting polymer from the porous TiO2 film. The cell power conversion efficiency could be further improved by optimizing the in-situ polymerization conditions, polymer structures, film morphologies, and contacts of metal/polymer/inorganic interfaces.

並列關鍵字

TiO2/Conjugated polymer composites ； electrochemical polymerization ； Fe3O4/PAA composites ； photovoltaic application

參考文獻

Chapter 1

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