【作者】 王艳荣；

【导师】 曹少魁；

【作者基本信息】 郑州大学 ， 材料学， 2011， 博士

【摘要】 随着化石能源的消耗和人们环保意识的加强,太阳能作为一种真正意义上的绿色能源引起了人们的高度重视。基于光生伏打效应的太阳能电池是开发和利用太阳能的最有效方法之一。在目前常用的太阳能电池材料中,聚合物太阳能电池因具质量轻,成本低和易大面积加工的特点而成为当今国际社会研究关注的热点。而聚合物的光吸收与太阳光谱不匹配,载流子迁移率较低以及材料的稳定性较差等是造成聚合物太阳能电池性能相对较差的主要原因。聚酰亚胺是一类具有很高热稳定性(一般玻璃化转变温度Tg高于200℃)、光化学稳定性较高、同时又具有电子给体／受体交替主链等特点的材料。本文通过分子设计,将金属钉配合物引入聚酰亚胺的主链或侧链以拓宽其光吸收性能；在主链中引入具有庞大侧基笏的9,9-二苯基芴二胺(FBPA)或三苯胺二胺单体M2(tpa)制备热稳定性和光化学稳定性较高、在可见光区有较强的光吸收、并具有较大电荷迁移率的新型聚合物光伏材料。1、首先合成了两个含螫合配体(L)二胺单体M1(bpy)和M3(tpa(bpy))；然后M1、M3和FBPA或M2以1：0,3：1,1：1,1：3的比例与含氟二酐(6FDA)通过“高温一步法”进行共缩聚,合成了主链或侧链含联吡啶螫合配体和空穴传输基团的新型聚酰亚胺LHPI-1(bpyx.-FBPA-PI)(x：含螯合配体二胺占二胺单体的摩尔分数)、LHPI-2(bpyx-tpa-PI)和LHPI-3[tpa(bpy)χ-tpa-PI]；通过"一锅煮’的方法,LHPI-1、LHPI-2和LHPI-3与钉金属配合物(Ru-complex)配位得到主链或侧链含金属配合物和空穴传输单元的聚酰亚胺DHPI-1、DHPI-2和DHPI-3。1H-NMR、IR、元素分析、GPC的表征结果表明,所得到的单体和聚合物与设计的化学结构一致。2. DHPI-1、DHPI-2和DHPI-3在高沸点、强极性溶剂DMSO、DMF等中具有较好的溶解性；在THF、CHCl3等低沸点、极性溶剂中的溶解性随着FBPA和tpa含量的增加而增加。TG表征结果显示LHPI和DHPI都有较好的热稳定性。通过UV-Vis吸收光谱表征结果显示金属钌配合物的引入将DHPI-1、DHPI-2和DHPI-3的吸收边带拓宽到了750 nm左右,有利于聚合物捕获可见光区的太阳光子。FL光谱表征结果显示,DHPI-1和DHPI-2的荧光强度除了bpy25Ru-tpa-PI之外荧光强度明显弱于相应的LHPI-1和LHPI-2,说明金属钉配合物对聚合物有荧光猝灭作用,荧光猝灭效应可以降低聚合物吸收光能的损失,有利于聚合物中激子的分离,提高光电转换效率；但是LHPI-3和DHPI-3具有几乎相同的荧光强度,也说明了侧链柔性挂接金属配合物不影响聚合物的光物理性能。3、通过循环伏安对LHPI-1、DHPI-1、tpa(bpy)100-PI和tpa(bpy)100Ru-PI的电化学性能进行了测试,结果表明,金属钉配合物的引入降低了聚合物的能带隙,提高了含金属钉配合物聚酰亚胺的给电子能力。4、以DHPI-1并(?)tpa(bpy)100Ru-PI或者DHPI-1(或tpa(bpy)100Ru-PI)与PCBM的混合物作为光活性材料,制备了太阳能电池器件。对其光电响应特性进行了初步表征,电流密度-电压(J-V)关系曲线显示典型的二极管特性。初步优化结果显示器件结构为ITO/PEDOT:PSS/DHPI:PCBM(1:1)/Al的器件具有相对较好的光伏性能。其中以tpa(bpy)100Ru-PI:PCBM(1:1) (w/w)为光电活性层的器件ITO/PEDOT:PSS/tpa(bpy)100Ru-PI:PCBM(1:1)/Al的光伏性能较好,在55 mWcm-2光照下,其Voc为0.30 V,Jsc为100.1μA cm-2,FF为0.31和ηc。为1.71×10-2%,特别是cη。值从没有阳极修饰的单层器件(ITO/tpa(bpy)100Ru-PI:PCBM(1:1)/Al)的2.67×10-5%提高到1.71×10-2%。更多还原

【Abstract】 With the exhaustion of fossil energy resources and the increase of the environment consciousness of human beings, solar energy as a real sense of renewable and green energy sources has been paid much attention. Photovoltaic cells are one of attractive methods for harnessing inexhaustible clean energy from the sun. Polymeric solar cells (PSCs) have become a hot research topic over the past decade for their potential application in large-scale power generation based on materials that provide the possibilities of being flexible, light in weight and cheap in price. However, the power conversion efficiency (PCE) of PSCs needs to be improved for future commercial applications. The factors limiting the PCE of the PSCs include the low exploitation of the sunlight due to the narrower absorption band of the absorption spectra of polymers in comparison with the solar spectrum and the mismatch of the two spectra, and the low charge transport efficiency in the devices due to the low charge carrier mobility of polymer pbtotovoltaic materials. Therefore, the design and synthesis of polymers with broad absorption and high charge carrier mobility was an effective way to improve the power conversion efficiency.Polyimides have been proven to be very stable to thermal, chemical and photophysical actions. Polyimide chains consist of alternating electron acceptor diimide fragments (A) and electron donor arylene rests of starting diamines (D). Aiming to prepare photovoltaic materials with broad absorption, good thermal stability and high charge carrier mobility, we have proposed two stratagies in this paper. One of our efforts is to introduce ruthenium metal complex to extend the absorption in the visible region into polyimide main chain or side chain. And the other one is to introduce the cardo4,4’-(9H-fluoren-9-ylidene) bisphenylamine (FBPA) or 4,4’-diaminotriphenylamine (tpa) as hole transporting moieties (HTM) by copolycondensation to improve the solubility, thermal stability and charge carrier mobility into polyimide main chain. With such a molecular design, the light harvesting ability of ruthenium complexes would be combined with the excellent thermal stability of polyimide in one molecule. Firstly, two monomers M1 (bpy) and M3 [tpa(bpy)] containing bipyridine ligand (L) were synthesized. Then, the three series of polyimides, which were named LHPI {LHPI-1 (bpyx-FBPA-PI) (x:mol%of diamine containing bipyridine ligand), LHPI-2 (bpyx-tpa-PI), and LHPI-3 [tpa(bpy)x-tpa-PI]}, were prepared by the cololymerization of 4,4’-(Hexafluoroisopropylidene)-diphthalic anhydride (6FDA) with two diamine monomers in different ratio. These polyimides were synthesized by a one-step polymerization in m-cresol with isoquinoline as catalyst at 200℃and purged with argon flow. Then, the polyimides containing ruthenium complexes DHPI (DHPI-1, DHPI-2, and DHPI-3) were synthesized by the reaction LHPI with ruthenium complex using a "one-pot" method. The difference of DHPI-1, DHPI-2 and DHPI-3 is that the Ru-complexes of the former is in the main chain of polyimides, the later is on the side chain. The chemical structures of the monomers and polymers were confirmed by1H NMR, IR, and elemental analysis. The Mn of the ligand polymer LHPI was measured by GPC.LHPI and DHPI showed good solubility in common aprotic organic solvents such as DMSO and DMF. While, DHPI showed somewhat poorer solubility than LHPI, especially in low boiling point solvents, such as CHCl3 and THF. And, the solubility were increased with increasing the FBPA or tpa unit content. These copolyimides containing ruthenium complexes were thermaly stable as measured by TG analysis. UV-Vis measurements revealed that DHPI exhibited very broad absorptions in the range 350-750 nm due to the introduction of ruthenium complexes. Such absorption enhancement would enable the polymer to harvest solar light in the visible region. The fluorescence spectra of all polyimides solution were investigation. The results showed that the emissions from polyimides containing Ru-complexes in the main chains were quenched signigicantly compared with metal-free polymers. This may be due to the presence of an energy transfer process from the main chain to the ruthenium complex with lowlying energy levels, which could reduce the loss of polymer absorption sunlight energy, facilitate separation of excitons, and improve photoelectric conversion efficiency. While, the emissions from polyimides containing Ru-complexes on the side chains had the same fluorescence intensities with their corresponding to metal-free polyimides. The onset oxidation potential of DHPI-1 and tpa(bpy)100Ru-PI were lower than that of LHPI-1 and tpa(bpy)100-PI as measured by cyclic voltammetry. This result suggested that the introduction of Ru-complexes made the DHPI easier to oxidize than the ligand polymer LHPI. The band gaps of DHPI-1 and tpa(bpy)100Ru-PI were 1.55-1.77 eV, which were narrower than that of polyimides of metal free, LHPI-1 and tpa(bpy)100-PI.Polymer photovoltaic cells were fabricated by using DHPI-1 and tpa(bpy)100Ru-PI or the blend of DHPI-1 (or tpa(bpy),ooRu-PI) and PCBM as the photoactive materials. Current density-voltage (J-V) measurement of the devices showed a typical rectifying behavior under a 55 mW cm-2 compact white arc lamp. The results showed that pure polymers in all cases exhibited very poor photovoltaic performances, which may be result from the molecular internal lower carrier mobility of polyimide. The structure, ITO/PEDOT:PSS/DHPI:PCBM(1:1)/Al, showed better Photovoltaic Properties. Especially, when the blend tpa(bpy)100Ru-PI and PCBM (1:1) (w/w)as the photoactive material, the performances of device were best compared with other same structure devices. The Voc, Jsc, FF, andηe were 0.30 V,100.1 uA/cm2,0.31 andηe 1.71×10-2%, respectively. Optimization in device structure and molecular design will be a part of our future work for the improvement of device performance with materials combining polyimide and ruthenium complexes.更多还原