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|其他題名: ||Fabrication of Plastic Photoanodes by Electrophoresis and Mechanical Compression for Applications in Dye-Sensitized Solar Cells|
Lung-Chuan Chen;Fu-Ren Tsai
scattering layer;electrophoresis;sulfuric acid;ITO-PEN;titanium dioxide;dye-sensitized solar cells;mechanical compression
|Issue Date: ||2020-03-24 11:12:28 (UTC+8)|
|Abstract: ||本文利用刀刮、電泳及機械壓力等程序於室溫在銦錫氧化物/聚萘二甲酸乙二酯(ITO/PEN)導電基板上沉積層次化的二氧化鈦，做為染料敏化太陽能電池的陽極薄膜，討論程序變數對薄膜性質及電池效率的的影響。第一部分探討塑膠導電基板經不同pH值的硫酸水溶液酸洗後對其性質及應用在染料敏化太陽能電池(dye sensitized solar cells, DSCs)效率的影響。結果顯示ITO-PEN基板經酸洗後表面型態會改變，在高濃度的酸液中ITO會因蝕刻現象而有剝落的現象。ITO-PEN基板經XRD分析顯現強的二氧化錫結晶繞射峰，但缺乏典型的ITO或氧化銦繞射峰。在pH=1.8的硫酸水溶液酸洗10分鐘後，ITO-PEN基板的可見光透光率有明顯增加的現象。ITO-PEN基板的水接觸角會因為酸洗pH值降低及酸洗的時間增長而下降，表示基板的親水性增加。以酸洗的ITO-PEN基板進行DSCs實驗，結果顯示pH=3.8的效果最好，pH=5.8的效率與未酸洗者相差不大，pH=1.8則效果最差。不同pH值酸洗基板DSCs的光電轉換效率的差異主要是由光電流造成；光電壓及填充因子對效率的影響並不顯著，而且酸洗程序對二氧化鈦薄膜吸附染料的影響並不顯著。本研究第二部分討論於ITO/PEN導電塑膠基板上，使用刀刮法沉積1或2層P25，再於其上以電泳法沉積粒徑較小的P90二氧化鈦(做為連結劑)，最後電泳粒徑約160nm的ST41二氧化鈦作為散射層，制備不同層次化的塑膠陽極染料敏化太陽能電池，討論電泳連結劑及散射層變化、電泳時間、及機械壓力大小對電極薄膜性質及DSCs效能的影響。電子顯微鏡分析指出，電泳 P90二氧化鈦可以填補薄膜的空隙，作為有效的連結劑，而大顆粒二氧化鈦散射層則會增加薄膜內部的反射性及降低光線的穿透率。分段刀刮-電泳製備的薄膜(樣品PEPE)比起一次性的刀刮-電泳程序獲得的薄膜(樣品P2E)顯示較低的光電轉換效率且有較低的電子蒐集效率。電化學阻抗分析顯示適當電泳P90二氧化鈦能降低薄膜內電子傳遞阻力。過度的電泳會導致過量的二氧化鈦沉積於薄膜表面，反而導致薄膜於壓力處理時形成縫隙，降低效率。薄膜機械處理的壓力對薄膜性質及光電轉換效能亦有明顯的影響，10MPa無法得到緻密的型態，而80MPa時壓力太大，造成擴散阻力的增加或薄膜表面縫隙的增加，而使效率降低，本系統的最適壓力約在50MPa。|
Room temperature procedures were developed to fabricate hierarchical titanium dioxide porous film on conductive indium-tin oxide (ITO)-coated polyethylene naphthalate (PEN) substrates consisting of a doctor blade technique and/or an electrophoresis method, followed by the mechanical compression for dye sensitized solar cells. The influence of acid-treatment on the properties of ITO-PEN plastic substrates and on the performance of the DSCs based on these acid-treated substrates is examined firstly. Results indicate that acid-treatment can partly etch away ITO components from PEN substrates, particularly in the strongly acidic solution. XRD analysis reveals strong SnO2 diffractive peaks, in contrast, the peaks originated from indium-tin-oxides and indium oxides are very insignificant for the commercial ITO-PEN films. Increment in transmittance of the ITO-PEN substrate can be observed after soaking in the sulfuric acid solution of pH 1.8 for 10 min. The contact angle of water decreases with decreasing pH value and increasing soaking time, which is indicative of increased hydrophilic property. Photovoltaic measurement of DSCs based on the acid-treated ITO-PEN substrates indicates that power conversion efficiency decreased in order of pH3.8 > pH 5.8 ~ un-treatment > pH1.8, which can be predominantly ascribed to the enhanced photocurrent resulted from the improved contact between TiO2 particles and ITO-PEN substrates. The photo-voltage, fill factor, and dye adsorption show insignificant influence on the power conversion efficiency.The second part of this research is to study the influence of hierarchical structure fabricated by doctor blading P25 and electrophoresising P90 and/or ST41 titanium dioxide particles. The P25 and ST41 TiO2 particles are designed to act as active and scattering layers, respectively, while the P90 particles are the connecting agents to link P25 particles. Results reveal that deposited P90 TiO2 nanoparticles by electrophoresis can fill the cracks and enhance the inter-particle connection between P25 particles. The scattering layer of ST41 particles can increase the light reflectivity and reduce the transmittance. DSCs with films prepared by 2 cycles of doctor blade-electrophoresis procedures exhibit less efficiency and charge collection efficiency when compared with the one by a cycle of doctor blade-electrophoresis procedure under the same electric charge and current density. Electrochemical impedance spectra indicate that appropriate electrophoresis deposition of P90 can lower the electro-transport resistance within the TiO2 layer. However, extra electrophoresis may cause surplus P90 TiO2 deposited on the surface of P25 layer, which develops cracks on applying mechanical compression and then reduces power conversion efficiency. The compression pressure also exerts significant impact on the film morphologies and power conversion efficiency. 10 MPa is too low to form a compact film and 80 MPa is considered as an exceeding pressure that causes an increment in diffusion resistance of electrolyte and dye within the film. In addition, an extraordinary high mechanical pressure is suspected to destroy the ITO/PEN substrates and then lower the adhesive strength between the film and ITO/PEN substrate, diminishing power conversion efficiency. The optimum pressure in this study is around 50 MPa.
|Appears in Collections:||[光電工程系所] 博碩士論文|
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