發(fā)布時(shí)間：2018-09-12 07:58

【摘要】：當(dāng)前地球人口數(shù)量在逐年攀升，化石能源將無(wú)法滿(mǎn)足人類(lèi)日益增長(zhǎng)的能源需求。尋找并利用可再生能源是全球所關(guān)注和研究的熱點(diǎn)。在所有的可再生能源中，太陽(yáng)能是未來(lái)最有可能的能源供給方式，，其最主要的利用途徑是太陽(yáng)能發(fā)電。近年來(lái)，染料敏化太陽(yáng)能電池（Dye-sensitized solar cells, DSC）因其較低的生產(chǎn)成本與較高的光電轉(zhuǎn)換效率引起了人們的廣泛關(guān)注，并被認(rèn)為是最有潛力的第三代太陽(yáng)能電池。當(dāng)前，DSC的性能還無(wú)法與傳統(tǒng)晶體硅太陽(yáng)能電池相比擬，因此挖掘其性能上的潛力是一項(xiàng)重要而有意義的工作。當(dāng)今，大量研究者對(duì)DSC性能的研究多立足于材料、器件結(jié)構(gòu)等，很少涉及DSC的內(nèi)部物理機(jī)制。探尋DSC器件的物理機(jī)制對(duì)提升DSC性能有著重要的促進(jìn)作用。本文從DSC器件物理研究出發(fā)，提出了精確、有效的DSC物理機(jī)制分析方法與內(nèi)部物理參數(shù)測(cè)試方法，并以此為基礎(chǔ)探尋提高器件性能的有效途徑。 首先，基于DSC的等效電路模型，研究了影響DSC光電轉(zhuǎn)換效率的關(guān)鍵因素。利用單結(jié)等效電路模型，首次采用遺傳算法（Genetic Algorithm, GA）、粒子群算法（Particle Swarm Optimization, PSO）和差分算法（Differential Evolution, DE）分別對(duì)DSC的等效電路參數(shù)進(jìn)行了分析和提取。研究發(fā)現(xiàn)， PSO算法具有較高的參數(shù)精度、抗噪能力和計(jì)算效率，是一種準(zhǔn)確、高效的DSC參數(shù)提取方法。該方法有效解決了DSC器件參數(shù)精確提取的技術(shù)難題。通過(guò)對(duì)電路參數(shù)的精確提取，發(fā)現(xiàn)DSC的內(nèi)部串聯(lián)電阻Rs是影響器件性能的重要參數(shù)之一。因此，要實(shí)現(xiàn)DSC更高的光電轉(zhuǎn)換效率，必須研究降低器件Rs值的有效方法，這為DSC的研究工作指明了方向。 其次，研究了通過(guò)抑制復(fù)合反應(yīng)提高DSC性能的器件物理機(jī)制。復(fù)合反應(yīng)速率與DSC的能量轉(zhuǎn)換效率密切相關(guān)，通過(guò)抑制復(fù)合反應(yīng)能有效提升光陽(yáng)極中的有效電子濃度，提高擴(kuò)散電流密度，增強(qiáng)光陽(yáng)極中的電子輸運(yùn)能力，亦即降低電池中的Rs。為定量研究復(fù)合反應(yīng)與光陽(yáng)極中有效電子濃度的對(duì)應(yīng)關(guān)系，需對(duì)光陽(yáng)極中自由電子壽命進(jìn)行準(zhǔn)確測(cè)量和分析。作為表征復(fù)合反應(yīng)最重要的參數(shù)，通常的測(cè)量方法和數(shù)據(jù)處理都比較復(fù)雜。本文結(jié)合瞬態(tài)光電測(cè)試方法和Savitzky-Golay濾波技術(shù)，提出采用可變級(jí)微分平滑方法分析計(jì)算DSC中的電子壽命。該研究首次實(shí)現(xiàn)了對(duì)DSC電子壽命的精確、高速測(cè)量，為定量表征DSC的內(nèi)部復(fù)合機(jī)制提供了一種可靠的方法。 再次，提出了基于稀土元素?fù)诫s的新型氧化物半導(dǎo)體DSC光陽(yáng)極材料，并對(duì)材料的電學(xué)、光學(xué)性能進(jìn)行了數(shù)值模擬。通過(guò)第一性原理計(jì)算，發(fā)現(xiàn)經(jīng)稀土元素La摻雜的ZnO材料自由電子密度增加，呈現(xiàn)金屬化特性，有效增強(qiáng)了光陽(yáng)極的電子輸運(yùn)和收集能力，降低了光陽(yáng)極電阻。同時(shí)，La摻雜后ZnO帶隙變寬，吸收邊藍(lán)移，拓寬了光陽(yáng)極的透射波段，減少了入射光損失，材料的光吸收率、光反射率也有所降低。這些都有利于提升光吸收層中的入射光子數(shù)量，從而實(shí)現(xiàn)器件更高的輸出電流和能量轉(zhuǎn)換效率。該研究不但揭示了一條提高DSC光電轉(zhuǎn)換效率的有效途徑，還揭示了ZnO作為DSC光陽(yáng)極材料具有很大的應(yīng)用潛力。 最后，提出了利用光學(xué)運(yùn)籌的方法，通過(guò)調(diào)控光陽(yáng)極界面來(lái)提高DSC的性能。采用光化學(xué)催化法在TiO2光陽(yáng)極鍍上薄層銀納米顆粒，通過(guò)控制光催化鍍銀時(shí)間以調(diào)節(jié)納米顆粒的覆蓋量。銀納米顆粒的散射增大光在光陽(yáng)極中的有效傳輸距離，提升了太陽(yáng)光利用率，提高了器件的短路電流密度。降低TiO2納米顆粒的表面態(tài)密度，將減緩光生電子與電解液中氧化物的復(fù)合反應(yīng)，改善光生電子在介孔TiO2薄膜內(nèi)的傳輸，從而降低內(nèi)部串聯(lián)電阻Rs。研究結(jié)果表明，利用該方法，DSC的光電轉(zhuǎn)換效率由5.97％提升至6.86％。該研究所提出的DSC光陽(yáng)極界面調(diào)控技術(shù)，能有效提高器件的光電轉(zhuǎn)換效率，并對(duì)DSC設(shè)計(jì)工作有重要的指導(dǎo)意義。
[Abstract]:As the population of the earth is increasing year by year, fossil energy will not be able to meet the increasing energy demand of mankind. Searching and utilizing renewable energy is the focus of global concern and research. In recent years, dye-sensitized solar cells (DSCs) have attracted much attention due to their low production costs and high photoelectric conversion efficiency, and are considered as the most promising third generation solar cells. The potential of DSC performance is an important and meaningful work. Nowadays, a large number of researchers focus on the material, device structure and so on, seldom on the internal physical mechanism of DSC. Effective DSC physical mechanism analysis method and internal physical parameter measurement method are used to explore effective ways to improve device performance.
Firstly, based on the equivalent circuit model of DSC, the key factors affecting the photoelectric conversion efficiency of DSC are studied. Using the single-junction equivalent circuit model, genetic algorithm (GA), particle swarm optimization (PSO) and differential evolution (DE) are used for the first time to improve the equivalent circuit parameters of DSC respectively. It is found that PSO algorithm is an accurate and efficient method for extracting DSC parameters with high precision, anti-noise ability and computational efficiency. This method effectively solves the technical problem of precise parameter extraction of DSC devices. Therefore, in order to achieve higher photoelectric conversion efficiency of DSC, it is necessary to study effective methods to reduce the Rs value of the device, which points out the direction of DSC research.
Secondly, the mechanism of improving DSC performance by restraining recombination reaction is studied. The recombination reaction rate is closely related to the energy conversion efficiency of DSC. By restraining recombination reaction, the effective electron concentration in the photoanode can be effectively increased, the diffusion current density can be increased, and the electron transport capacity in the photoanode can be enhanced, that is, the Rs in the battery can be reduced. In order to quantitatively study the relationship between the composite reaction and the effective electron concentration in the photocathode, it is necessary to measure and analyze the free electron lifetime of the photocathode accurately. As the most important parameter to characterize the composite reaction, the usual measurement methods and data processing are very complicated. A variable-order differential smoothing method is proposed to analyze and calculate the electron lifetime in DSC. This study is the first time to achieve accurate and high-speed measurement of the electron lifetime of DSC, and provides a reliable method for quantitatively characterizing the internal recombination mechanism of DSC.
Thirdly, a new type of oxide semiconductor DSC photoanode material based on rare earth element doping is proposed, and the electrical and optical properties of the material are simulated numerically. At the same time, the band gap of ZnO doped with La becomes wider, the absorption edge blue shifts, the transmission band of the anode is widened, the loss of incident light is reduced, the optical absorptivity and the optical reflectivity of the material are also reduced. This study not only reveals an effective way to improve the photoelectric conversion efficiency of DSC, but also reveals the potential application of ZnO as a DSC anode material.
Finally, a method of optical operation research is proposed to improve the performance of DSC by adjusting the interface between the photocathode and the anode. A thin layer of silver nanoparticles is deposited on the titanium dioxide photocathode by photochemical catalysis, and the coverage of the nanoparticles is adjusted by controlling the time of photocatalytic silver plating. The utilization ratio of sunlight is increased, the short circuit current density of the device is increased, the surface state density of the nanoparticles is decreased, the composite reaction between photogenerated electrons and oxides in the electrolyte is slowed down, the transmission of photogenerated electrons in the mesoporous TiO2 film is improved, and the internal series resistance Rs is reduced. The conversion efficiency is improved from 5.97% to 6.86%. The proposed DSC photoanode interface control technology can effectively improve the photoelectric conversion efficiency of the device, and has important guiding significance for DSC design.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TM914.4

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