【作者】 陈伟；

【导师】 陈义旺； 李璠；

【作者基本信息】 南昌大学 ， 有机化学， 2012， 硕士

【摘要】 近年来,新兴可替代太阳能光伏技术,例如染料敏化太阳能电池(DSSCs)和有机太阳能电池(OSCs),由于具有许多优良特性已经引起了全世界科学研究者极大的关注。有机太阳能电池当中的杂化本体异质结太阳能电池是由有机共轭聚合物和无机纳米晶材料混合构成电池的光活性层。有机无机杂化太阳能电池能够同时具有有机共轭聚合物可溶液加工性、高吸收效率和无机纳米晶的高迁移率、制备简单、化学稳定性好等优点。但是,到目前为止,杂化太阳能电池的光电转换效率要低于全有机型太阳能电池器件。在众多影响杂化太阳能电池效率的因素中,杂化太阳能电池活性层纳米级微观形貌是其中最为关键的因素。液晶性物质具有极强的自组装能力,在一定条件下能够形成有序的液晶相微观结构。利用液晶性材料优越的形貌控制能力调控有机无机杂化太阳能电池的异质结界面及微观结构,不仅可以实现D材料和A材料在纳米尺度上的相分离,而且还可以提高整个活性层纳米复合材料微观结构的有序性,从而利于激子分离、电荷转移以及输运,进而提高器件光电转换效率。本论文首先设计合成了一种新型的电子给体材料-侧链含有氰基联苯基团的聚噻吩poly[3-(6-(4-cynaobiphenyloxy)-hexyl) thiophene](P3HbpT),并用它作为聚合物/ZnO纳米粒子杂化太阳能电池的电子给体。氰基联苯自发组装性质能够赋予液晶聚合物P3HbpT良好的有序微观形貌,并且能促使ZnO纳米粒子在聚合物体系中均匀分散。实验结果表明,液晶态退火处理之后(175℃),液晶聚合物、P3HbpT/ZnO复合薄膜对太阳光吸收能力增强,聚合物分子链排列结构有序性提高。此外,液晶聚合物P3HbpT在液晶态温度热处理之后,由于液晶基元自发组装特性能够诱导ZnO纳米粒子形成具有高度有序的纳米聚集结构。同时,为了研究液晶聚合物P3HbpT诱导取向特性对聚合物/ZnO杂化太阳能电池器件性能影响,本文制备了以P3HbpT/ZnO为活性层的杂化太阳能电池,与无退火和低于液晶态温度(120℃)退火后的器件性能相比,液晶态温度热退火处理之后的器件性能达到最优,光电转换效率达到了0.61%,填充因子和短路电流也明显提高。实验表明,液晶态退火处理后的P3HbpT/ZnO杂化太阳能电池性能提高是因为液晶态温度下热退火能够形成微观形貌有序的活性层,从而有利于激子产生和分离,同时电荷传输效率也极大增强,最终导致太阳能器件性能提高。随后,为了拓宽活性层对太阳光的吸收范围,本文还设计合成了一种新型的窄带隙D-A型液晶共轭聚噻吩衍生物-poly[3-(6-(cyanobiphenyoxy)thiophene)-alt-4,7-(benzothiadiazole)](P3HbpT-BTD),对该聚合物在不同热处理条件下的纳米结构和光电性质进行了系统的研究。研究发现,在液晶态温度退火处理后,聚合物侧链上氰基联苯液晶基元能够诱导聚合物主链自组装成有序的层状纳米结构。同时,还研究了液晶聚合物P3HbpT-BTD/ZnO纳米复合薄膜在各种温度热处理后的微观形貌变化,并考察退火温度对活性层微观形貌的影响。研究发现,在高于或者低于液晶态温度区间退火处理后,复合薄膜中的聚合物链段有序性急剧降低,并引起ZnO纳米粒子较大面积的团聚。然而P3HbpT-BTD/ZnO复合薄膜经过液晶态温度(180℃)退火之后,ZnO纳米粒子能够形成良好分散和高度取向的纳米级自组装区域。研究表明,聚合物在液晶态下的自发组装取向能够诱导ZnO纳米粒子在一定范围内取向,并且能够增强ZnO纳米粒子的结晶性,从而极大的提高电子迁移能力。因此,P3HbpT-BTD/ZnO复合薄膜在液晶态温度热退火之后能够形成纳米级的相分离微观结构,从而能够形成非常有序的互穿网络结构。随后进一步研究了以P3HbpT-BTD/ZnO复合薄膜作为活性层的杂化太阳能电池器件性能与热处理条件的相互关系。经对比实验结果表明,在液晶态温度区间退火处理之后的器件性能达到最优,光电转换效率达到了1.98%。因此,利用液晶共轭聚合物液晶态下自发组装特性,能够有效控制电池活性层的微观形貌,并极大地提高器件性能。最后,为了有效控制有机无机杂化太阳能电池界面形貌和光活性层微观结构,本文设计合成了一种新型的小分子液晶半导体配体4-(5-(1,2-dithiolan-3-yl)pentanoate)-4’-(hexyloxy)-terpheny1(HTph-S),并用该液晶配体修饰ZnO纳米粒子表面,形成HTph-S@ZnO复合纳米粒子,再用该复合纳米粒子作为太阳能电池电子受体,P3HT作为电子给体制备杂化太阳能电池,考察液晶配体HTph-S对P3HT/ZnO杂化太阳能电池活性层界面修饰后对光活性层微观形貌、光学性质以及活性层中激子分离和电荷转移效率的影响。透射电子显微镜和光学性能研究表明,经过半导体液晶配体修饰之后,ZnO纳米粒子和聚合物相容性明显增强。ZnO/P3HT复合薄膜经液晶态温度条件退火处理之后,聚合物P3HT结晶性和有序性明显提高,同时液晶配体的诱导取向特性能够诱导ZnO纳米粒子趋于类一维有序排列结构,从而能够与聚合物一起形成良好的互穿网络微观结构,进而有利于电子和空穴传输,相应的杂化太阳能器件性能也明显增强。在配体液晶态温度(120℃)热退火之后,器件最优光电转换效率达到了1.23%。更多还原

【Abstract】 Emerging alternative photovoltaic technologies such as dye sensitized solar cells (DSSCs) and organic solar cells (OSCs) have recently gained much attention as well as maturity and are on the step of being commercialized. To date, bulk heterojunction hybrid solar cells containing inorganic nanoparticles and semiconducting polymers are still lagging behind in respect of device performance although they can combine combining the advantages of both types of materials: solution processability and high absorption of semiconducting polymers, high electron mobility, and good chemical stability of inorganic semiconductor nanocrystals. Among the various factors impacting the photovoltaic performance of bulk heterojunction hybrid solar cells, the nanoscale morphology or microstructure of the active layer in hybrid solar cells is critical to ensure the high devices performance.Liquid crystalline materials with powerful self-assembly abilities can form ordering liquid crystalline microstructure under its LC state. Utilizing the LC materials’ excellent orientation abilities to control the morphology and D-A interfaces of active layers of bulk-heterojunction hybrid solar cells not only achieve the nanoscale phase separation of D-type and A-type materials, but also improve the microstructure ordering of nanocomposites in active layers, which can effectively facilitate the exciton separation, charges transferring and transportation, improve the photovoltaic performances of hybrid solar cells.In this dissertation, firstly, a novel electron-donor material, liquid-crystalline polythiophene containing a cyano-biphenyl mesogenic pendant, poly[3-(6-(4-cynaobiphenyloxy)-hexyl)thiophene](P3HbpT), was rationally designed and synthesized. The spontaneous orientation of cyano-biphenyl mesogen endowed the P3HbpT with a well ordered morphology and facilitated the homogeneous dispersion of ZnO nanoparticles in the composites. The P3HbpT/ZnO composite films exhibited red-shift absorption (12nm), the lower LUMO and more ordered domains after undergoing annealing at liquid crystal (LC) states temperature (175℃), which indicated that the spontaneous assembly behavior of the liquid-crystalline polythiophene could induce the ZnO nanoparticles to form nano-dispersing structure with highly oriented channel layers upon heating at liquid crystalline states. Furthermore, the hybrid bulk-heterojunction devices based on P3HbpT/ZnO active layer have been constructed. Without extensive optimization, the devices undergoing annealing at LC state yielded a Voc of0.83V and power conversion efficiency (PCE) of0.61%, showing a significantly increased Jsc and FF with respect to the un-annealed counterpart.Secondly, A new donor-acceptor type liquid-crystalline copolymer, poly[3-(6-(cyanobiphenyoxy)thiophene)-alt-4,7-(benzothiadiazole)], P3HbpT-BTD, via copolymerization of liquid-crystalline electron-donating thiophene units and electron-accepting benzothiadiazole (BTD) units was designed and synthesized successfully. The nanostructure and photoelectric properties of the copolymer under different thermal treatment conditions were systematically investigated. Studies of the relationship between the annealing conditions and the nanostructures of the copolymer revealed that the cyano-biphenyl mesogenic units could induce the copolymer chains into a well ordered lamella structure upon annealing at liquid crystalline states temperature. When the hybrid films of P3HbpT-BTD/ZnO NPs were annealed at the temperature below or above the mesophase temperature region, less ordered copolymer chains brought an undeveloped interpenetrating network and caused the large aggregation of ZnO NPs. Most strikingly, the hybrid film annealed at liquid-crystalline state temperature (180℃) achieved the well-dispersed and high orientated nanoscale assembled nanoparticles regions. The spontaneous self-organization of P3HbpT-BTD enhanced the crystallinity and orientation of the ZnO NPs. Therefore, the resulting nanoscale phase separation of the hybrid films leaded to well-ordering percolated networks. Hybrid bulk heterojunction photovoltaic devices based on copolymer P3HbpT-BTD and ZnO NPs were fabricated under different annealing treatment. A best power conversion efficiency of1.98%was achieved upon annealing at mesophase temperature (180℃). Lastly, Liquid crystalline ligand,4-(5-(1,2-dithiolan-3-yl)pentanoate)-4’-(hexyloxy)-terphenyl (HTph-S), were employed as the semiconducting interface modification material for the fabrication of ZnO nanoparticles/P3HT hybrid solar cells. The HTph-S has a dithiolane ring which can attach to the surface of ZnO nanoparticles and the terphenyl aromatic group with hexyloxy end chain, which should make the ZnO nanoparticles miscible with conjugated polymers. A best power conversion efficiency of1.23%was achieved under an AM1.5G (100mW cm-2) condition after thermal treatment at LC state temperature (120℃). The enhanced performance of hybrid solar cells may mainly be accounted for the improved compatibility, enhanced charge separation and transfer efficiency and optimized micro-morphology of the ZnO/P3HT hybrid films induced by the self-organizing behavior of HTph-S ligands in its LC state.更多还原