【作者】 应伟江；

【导师】 花建丽；

【作者基本信息】 华东理工大学 ， 应用化学， 2013， 博士

【摘要】 染料敏化太阳能电池(DSSCs)是利用染料敏化剂吸收太阳光,从而将太阳能转化为电能的一种新型太阳能电池,具有成本低、制作工艺简单、光电转换效率较高等优势,引起了全世界的广泛关注。如何提高有机染料敏化太阳能电池的光电转换效率和稳定性是目前DSSCs研究的两个关键问题。本论文通过引入三种不同的额外缺电子基团,合成了五个系列以芳胺为电子给体的D.A-π-A型染料以及吡啶为吸附基团的染料,并将其应用于染料敏化太阳能电池中,系统地测试了其光电性能,并对其器件性能进行了优化。第一章,简要介绍了染料敏化太阳能电池的结构和工作原理、纳米晶半导体电极、电解质和对电极的发展状况,综述了近几年来具有高光电转换效率的D-A-π-A型有机敏化染料的研究进展,在此基础上提出了本论文的设计思路和研究内容。第二章,将窄能隙的异靛蓝引入到小分子染料敏化剂中,设计并合成了以三苯胺为给体,异靛蓝为辅助受体,噻吩(呋喃、苯)为π-链、氰基乙酸为受体的六个新型的具有D-A-π-A结构的染料敏化剂(ID1-ID6),并对其进行了核磁共振氢谱、碳谱和高分辨质谱的表征。通过光物理性能的测试,发现该系列化合物都有较宽的吸收光谱,部分化合物在TiO2膜上的光电响应甚至延伸至近红外区域(波长大于780nm)；电化学性能测试表明给体和π-链的改变可以方便调节HOMO和LUMO能级。在AM1.5(100mW cm-2)光强条件下,基于ID1-ID6染料敏化太阳能电池的光电转换效率为3.33-5.35%。通过改变CDCA的浓度对器件的性能进行优化,浓度为20mM的CDCA共吸附的ID6敏化电池获得最高光电转换效率为5.98%(Jsc=14.77mA cm-2,Voc=644mV,ff=0.63).电化学交流阻抗谱测试进一步证实：在异靛蓝染料中添加适当浓度的CDCA可以减少电子的复合,延长电子寿命,提高开路电压。第三章,为了进一步拓宽异靛蓝染料敏化剂的吸收光谱,提高摩尔消光系数,增大开路电压,设计合成了吲哚啉为给体、2-乙基己基叉链取代的异靛蓝为额外受体、噻吩(呋喃、苯)为π-链、氰基乙酸为受体的新型D-A-π-A结构的染料敏化剂(ID7-ID9)。研究发现,强给体的引入使染料的吸收光谱红移,增大了短路电流；2-乙基己基叉链的引入,减少了染料的聚集,有效阻止了电荷的复合,提高了开路电压。在AM1.5(100mW cm-2)光强条件下,基于ID7染料敏化的电池最大光电转换效率达到5.83%(短路电流为13.58mA cm-2,开路电压为602mV,填充因子为0.71)。第四章,设计合成了一系列吡啶并[3,4-b]吡嗪(PP)为辅助受体、含有不同给体和不同π-链的D-A-π-A型染料敏化剂(PP-I和APP-Ⅰ～Ⅳ)与PP核相比,甲氧基苯取代的APP能增加电池的短路电流和开路电压；在APP-Ⅰ～Ⅳ体系中,苯环的引入可以提高化合物的开路电压；三苯胺给体上引入辛氧基链不仅能使染料光谱拓宽,增大短路电流,还能提高开路电压。在AM1.5(100m W cm-2)光强条件下,APP-Ⅳ染料敏化的电池光电转换效率达到7.12%(短路电流为13.56mA cm-2,开路电压为691mV,填充因子为0.76)。此外,APP-Ⅳ染料还被应用于离子液体电解质电池,得到12.28mA cm-2的短路电流、0.648V的开路电压、0.76的填充因子和6.20%的光电转换效率,且在60C持续光照射1000小时,电池效率仍保持在97%,呈现了很好的稳定性。第五章,为了进一步提高电池的开路电压,把吡啶并吡嗪核上的甲氧基苯换成辛氧基苯,设计合成了一系列三苯胺为给体、辛氧基苯取代的吡啶并[3,4-b]吡嗪为额外受体、噻吩(呋喃、苯)为π-链、氰基乙酸为受体的D-A-π-A型染料敏化剂(OPP-Ⅰ～Ⅲ),并与染料APP-Ⅰ进行对比。实验结果表明,用辛氧基取代甲氧基,能有效减少染料在Ti02表面的聚集,同时能阻止电解质和Ti02导带的接触,抑制电荷复合,提高了开路电压。在AM1.5(100m W cm-2)光强条件下,OPP-Ⅰ敏化的电池最大光电转换效率为6.57%(短路电流为11.7mA cm-2,开路电压为717mV,填充因子为0.78)。第六章,将吸电子能力更强的[1,2,5]噻二唑并[3,4-c]吡啶(PT)作为辅助受体引入到染料中,合成了以三苯胺(二苯胺噻吩)为给体,PT为辅助受体，噻吩和苯为π-链的D-A-π-A结构染料敏化剂(PT1-PT4).研究了三苯胺和二苯胺噻吩给体、噻吩和苯共轭桥链对化合物吸收光谱、能级的影响。实验结果表明,给体或桥链改变可以调节染料的吸收光谱波长和能级。在AM1.5(100m W cm-2)光强条件下,PT1-PT4染料敏化的电池效率分别为2.40%,4.23%,0.64%和1.23%。二苯胺噻吩强给体的引入并没有达到预期效果,短路电流和开路电压都有不同程度下降。可能是由于其摩尔消光系数低和电荷复合快所致；此外,还对PT2进行器件优化,通过改变CDCA的浓度和电解质的配比来提高电池效率。研究发现,在LP和E1两种电解质条件下,加入一定量的CDCA能大大提高染料的短路电流和效率。使用LP电解质能一定程度提高开路电压但会引起短路电流的减小。最终,在E1电解质条件下,20mM的CDCA处理的PT2敏化电池获得最高效率6.11%(短路电流为12.61mA cm-2,开路电压为668mV,填充因子为0.74)。第七章,将新型受体吡啶(氰基吡啶)引入到染料中,合成了4个染料敏化剂(PY1-PY4)。测试了化合物的紫外吸收、电化学和光电性能。同时对吡啶上的氰基对染料性能的影响进行了讨论。实验结果表明,氰基的引入不仅能使染料吸收光谱拓宽,还能提高染料的摩尔消光系数。将PY1-PY4染料敏化的电池在AM1.5(100m W cm-2)光强下进行性能测定,PY1获得了2.14%的效率。虽然氰基取代的吡啶类染料电池有更高的短路电流,但是开路电压有所下降,总的光电转换效率值比PY1略低,进一步的器件优化测试正在进行中。更多还原

【Abstract】 Dye-Sensitized Solar Cells (DSSCs) is a type of solar cells which convert light to electricity by means of harvesting the solar irradiation by the sensitizers. DSSCs have attracted great worldwide attention due to their considerable efficiency and low cost, in which the sensitizer is deemed as the crucial component. To achieve high efficiency, the organic dyes are usually required to possess high charge carrier mobility, broad and intense spectral absorption and high stability. In this paper, several series of sensitizers have been designed and synthesized. Their photovoltaic performances have been studied in detail. In addition, a novel anchoring group of pyridine has been introduced into the organic dyes and has been studied.In chapter1, the definition of the structure and principle for the dye-sensitized solar cells, nanoporous semiconductor electrode, electrolytes and counterelectrode are introduced. Recent researches of D-A-π-A dye-sensitizers have been reviewed. Then the research strategy of the dissertation is presented.In chapter2, six new D-A-π-A sensitizers (ID1-ID6), withtriarylamine as the electron donor; isoindigo as an auxiliary electron withdrawingunit; thiophene, furan, and benzene as the linker; and cyanoacrylic acid as theanchoring group, were synthesized through simple synthetic procedures and with low cost. Their absorption spectra were broad with long wavelengthabsorption maximum approximately at589nm and the absorption onset at720nm on the TiO2film. Electrochemical experiments indicate that the HOMOand LUMO energy levels can be conveniently tuned by alternating the donormoiety and the linker. All of these dyes performed as sensitizers for the DSSCstest under standard global AM1.5solar light condition, and a maximum overall conversion efficiency of5.98%(Jsc=14.77mA cm-2, Voc=644mV,ff=0.63) is obtained for ID6-based DSSCs when TiO2films were first immersed for6h in20mM CDCA ethanol solution followed by12h of dipping in the dye CH2CI2solution. Electrochemical impedance measurement data implies that the electron lifetime can be increased bycoadsorption of CDCA, which leads to a lower rate of charge recombination and thus improved Voc.In chapter3, a series of new D-A-π-A organic dyes (ID7-ID9) containing indoline as electron donor have been synthesized, characterized, and used as the sensitizers for dye-sensitized solar cells (DSSCs). The influence of the donor and the2-ethyl-hexyl chain on isoindigo sensitizer and cell efficiency was studied. In comparison with the model dye ID1, these dyes containing indoline donor display broader absorption spectrum and higher molar extinction coefficient, which would enhance the short-circuit photocurrent density. Attaching the2-ethyl-hexyl chain in the middle of the isoindigo proved to be an effective means for reducing the π-π aggregation of the dyes on TiO2. Moreover, the steric hindrance of the banched chain successfully suppressed charge recombination and improved the open-circuit voltage. As a result, ID7-based DSSCs achieved a high overallconversion efficiency of5.83%(Jsc=13.58mA cm-2, Voc=602m V,ff=0.71) under standard global AM1.5solar light condition.In chapter4, a series of new pyrido[3,4-b]pyrazine-based organic sensitizers (PP-I and APP-I-IV) containing different donors and π-spacers have been synthesized and employed in dye-sensitized solar cells (DSSCs). It was found that APP-Ⅳ based DSSCs with liquid electrolyte display the highest power conversion efficiency (PCE) of7.12%. Importantly, a PCE of6.20%has been achieved for APP-IV based DSSCs with ionic-liquid electrolytes and retained97%of the initial value after continuous light soaking for1000h at60℃. This renders these pyrido[3,4-b]pyrazine-based sensitizers quite promising candidates for highly efficient and stable DSSCs.In chapter5, a series of new D-A-π-A sensitizers (OPP-Ⅰ-Ⅲ), with triarylamine as the electron donor, pyrido[3,4-b]pyrazine as the additional acceptor, thiophene and benzene as the linker and cyanoacrylic acid as the acceptor moiety has been synthesized to further improve the efficiency. The replacement of a methoxy group with anoctyloxy group can effectively reduce the π-π aggregation of the dyes on TiO2. Moreover, the steric hindrance of the octyloxy group successfully suppressed charge recombination and improved the open-circuit voltage (about80mV). OPP-Ⅰ-sensitized cell showedthe best conversion efficiency (PCE) of6.57%(Jsc=11.70mA cm-2, Voc=717m V, ff=0.78) under standard global AM1.5solar light condition.In chapter6, a series of new D-A-π-A sensitizer (PT1-PT4) containing [1,2,5]thiadiazolo[3,4-c]pyridine moiety were synthesized and used for dye-sensitized solar cells (DSSCs). Their absorption spectra, electrochemical and photovoltaic properties were fully characterized. Electrochemical measurement data indicate that the tuning the LUMO and HOMO energy levels can be conveniently accomplished by alternating the donor moiety. All of these dyes performed as sensitizers for DSSC test, PT2-sensitized cell treated with20mM CDCA showed the best conversion efficiency (PCE) of6.11%(Jsc=12.61mA cm-2, Voc=668mV, ff=0.74) under standard global AM1.5solar light condition.In Chapter7, a new anchoring group of pyridine (picolinonitrile) was introduced into the organic dyes, and four new dye sensitizers PY1-PY4were synthesized. Their absorption spectra, electrochemical and photovoltaic properties were fully characterized. The effect of the cyano group on photovoltaic performance was investigated. All of these dyes performed as sensitizers for DSSC test, PYl showed the best conversion efficiency (PCE) of2.14%(Jsc=6.49mA cm-2, Voc=509mV, ff=0.65) under standard global AM1.5solar light condition. Cyano-substituted pyridine dye (PY2) has a higher short-circuit current but the total value of the PCE is slightly lower than PYl because the open circuit voltage of PY2decreased, the further optimization is in progress.更多还原