Study of polymer solar cells.

• Other Authors: Wong, Man Kwong.
• Format: Others
• Language: English; Chinese
• Published: 2012
• Subjects: Photovoltaic cells > Materials; Polymers > Deterioration; Conducting polymers
• Online Access: http://library.cuhk.edu.hk/record=b5549202; http://repository.lib.cuhk.edu.hk/en/item/cuhk-328089

在這個對可再生能源需求不斷增加的新時代,聚合物太陽能電池成為其中一個最熱門的研究題目。在過去十年,聚合物太陽能電池的研究大多集中在液體處理的塊材異質接面結構。與傳統的‘雙層’結構比較,塊材異質接面結構提供一個更大的給體-受體界面面積讓電荷分離及減少電荷重組,從而帶來更高的能量轉換效率。目前使用塊材異質接面結構的聚合物太陽能電池最高能量轉換效率約為8 %。最近在文獻中公佈的一篇文章中,聲稱‘雙層’器件也可以達到與塊材異質接面器件媲美的高效率。這類‘雙層’器件採用相連沉積的給體層P3HT 和以二氯甲烷作溶劑的受體層PCBM 製作。然而,也有報告指在熱退火處理下PCBM 會擴散進入P3HT 的非晶區從而堤高能量轉換效率。我的工作是研究這類所謂的‘雙層’系統。藉運用紫外-可見光光譜儀和掠角X 光繞射,對埰用不同處理手法的純P3HT 薄膜的聚集和結晶性能進行研究。結果發現P3HT 的聚集和結晶性能可能沒有直接的相關性。同時也發現通過縮短底層P3HT 溶劑的揮發時間,這類液體鑄型‘雙層’器件的能量轉換效率得以提高。通過加熱P3HT 薄膜來加快變乾的速度,可以造具較低聚集度和較高結晶密度的P3HT 層。比起常規P3HT 薄膜可以提高能量轉換效率大約15 %。同時也對重量比為1:1 的複合P3HT:PCBM 薄膜的聚集和結晶性能進行了研究。實驗結果進一步表明P3HT 的聚集和結晶性能可能沒有直接的相關性。雖然實驗未有充分運用所有其他可能的處理方法和物理参數對器件進行全面優化,但這項研究卻為液體鑄型雙層聚合物太陽能電池開闢一條新的優化路線。 === In this new age with increasing demand of renewable energy sources, organic solar cell (OSC) has become one of the most intense research topics. The major attention of research in OSC was given to the solution-processed bulk heterojunction (BHJ) architecture during the past ten years. Compared to traditional ‘bilayer’ architecture, the BHJ structure provides a greater donor-accepter interface area for charge separation and reduced recombination, which leads to a higher power conversion efficiency (PCE). The highest PCE reported using BHJ was about 8 %. In a recent article published in the literature, it was claimed that ‘bilayer’ devices can also achieve a high efficiency comparable to that for BHJ devices. Such ‘bilayer’ devices were fabricated by sequential deposition of the donor P3HT and acceptor PCBM layers using dichlormethane as the solvent of PCBM. However, it was also reported that the PCBM could diffuse into the amorphous regions of P3HT during thermal annealing to cause the efficiency enhancement. My work is to study such so-called ‘bilayer’ system. By using UV-Visible spectrophotometer and grazing incidence XRD, the aggregation and crystallization properties of the pure P3HT films fabricated using different processing methods were studied. It was found that the P3HT aggregation may not have direct correlations with crystallinity. It is also discovered that the PCE of such solution-cast bilayer devices are increased by shortening the evaporation time of the underlying P3HT layer from a solution. By heating the P3HT film to accelerate its drying, a less aggregated P3HT layer with a higher density of crystallites could be obtained. The PCE could be enhanced by about 15 % over that using a regular P3HT film. The aggregation and crystallization properties of the composite P3HT:PCBM films with a ratio of 1:1 by weight were also studied. The experimental results further indicate that the P3HT aggregation may not have direct correlations with crystallinity. Although the devices have not been fully optimized by exhausting all the other possible processing and physical parameters, this study opens up a new route to optimize solution-cast bilayer polymer solar cells. === Detailed summary in vernacular field only. === Wong, Man Kwong = 聚合物太陽能電池研究 / 王文廣. === Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. === Includes bibliographical references. === Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. === Abstracts also in Chinese. === Wong, Man Kwong = Ju he wu tai yang neng dian chi yan jiu / Wang Wenguang. === Abstract --- p.I === 摘要 --- p.III === Acknowledgement --- p.VI === Chapter Chapter 1 --- Introduction to Organic Solar Cells --- p.1 === Chapter 1-1 --- The history of the development of solar cells --- p.1 === Chapter 1-2 --- Motivation of developing polymer solar cells --- p.2 === Chapter 1-3 --- The materials used in polymer solar cells --- p.4 === Chapter 1-4 --- Basic working principles of the polymer solar cells --- p.6 === Chapter 1-5 --- Definition of some important parameters of solar cells --- p.8 === Chapter 1-5-1 --- Short circuit current density (J[subscript Ssubscript C]) --- p.8 === Chapter 1-5-2 --- Open circuit voltage (V[subscript Osubscript C]) --- p.9 === Chapter 1-5-3 --- Fill factor (FF) --- p.10 === Chapter 1-5-4 --- Power conversion efficiency (PCE) --- p.11 === Chapter 1-6 --- An outline of this thesis --- p.12 === Chapter Chapter 2 --- Experimental Procedures --- p.13 === Chapter 2-1 --- Common preparation procedures in all the experiments --- p.13 === Chapter 2-1-1 --- The cleaning of the glass and indium tin oxide (ITO) substrates --- p.13 === Chapter 2-1-2 --- The preparation of different donor and accepter solution --- p.13 === Chapter 2-1-3 --- The coating of PEDOT:PSS on the glass and ITO substrates --- p.14 === Chapter 2-1-4 --- The thermal vapor deposition of the cathode layer for solar cell devices --- p.14 === Chapter 2-2 --- The detailed experimental procedures of the active layers in different chapters --- p.15 === Chapter 2-2-1 --- Fabrication of the active layers in chapter 3 --- p.15 === Chapter 2-2-2 --- Fabrication of the active layers in chapter 4 --- p.17 === Chapter 2-2-3 --- Fabrication of the active layers in chapter 5 --- p.18 === Chapter 2-3 --- Measurement of the properties of the film samples and the performance of the solar cells --- p.19 === Chapter 2-4 --- Experimental errors --- p.20 === Chapter Chapter 3 --- A Survey on Polymer Solar Cells and Some Preliminary Works --- p.21 === Chapter 3-1 --- Traditional bilayer polymer solar cells --- p.21 === Chapter 3-2 --- Bulk heterojunction polymer solar cells --- p.22 === Chapter 3-3 --- Studies of thermal annealing effects --- p.26 === Chapter 3-4 --- Studies of solvent annealing effects --- p.28 === Chapter 3-5 --- Studies of the relationship between the thickness and the optical density of the films --- p.34 === Chapter 3-6 --- Solution-cast bilayer polymer solar cells --- p.35 === Chapter 3-7 --- Previous studies on solution-cast bilayer polymer solar cells --- p.39 === Chapter Chapter 4 --- Studies on Solution-Cast Bilayer Polymer Solar Cells --- p.42 === Chapter 4-1 --- Motivation and the basic ideas of my research work --- p.42 === Chapter 4-2 --- Higher PCE through the use of a low pressure environment of film formation --- p.43 === Chapter 4-3 --- Higher J[subscript Ssubscript C] through the use of chloroform as the P3HT solvent --- p.46 === Chapter 4-4 --- Higher PCE through the use of a pre-dried heating process --- p.52 === Chapter 4-5 --- Dependence of the device performances on the pre-dried heating temperature --- p.55 === Chapter 4-6 --- Effect of a small amount of PCBM in the underlying P3HT layer --- p.59 === Chapter 4-7 --- Short summaries --- p.62 === Chapter Chapter 5 --- Studies on P3HT:PCBM Blend Layers --- p.64 === Chapter 5-1 --- Motivation --- p.64 === Chapter 5-2 --- Effects on the P3HT aggregation and crystallization of the P3HT:PCBM blend layers due to different treatments --- p.64 === Chapter 5-3 --- Studies of the effects of the removal of PCBM on the P3HT aggregation and crystallization in P3HT:PCBM blend layers --- p.67 === Chapter 5-4 --- Short summaries --- p.70 === Chapter Chapter 6 --- Conclusion --- p.71 === Chapter 6-1 --- Summaries of the research work --- p.71 === Chapter 6-2 --- Ideas for future studies --- p.72 === Bibliography --- p.74