节点文献

窄带隙共轭聚合物的制备与光伏性能研究

Synthesis and Photovoltaic Properties of Low-Bandgap Conjugated Polymers

【作者】 邓丹

【导师】 陈红征;

【作者基本信息】 浙江大学 , 高分子化学与物理, 2010, 博士

【摘要】 近些年来,聚合物太阳能电池由于能够采用低成本的溶液加工方法制备大面积柔性器件等优点而引起了人们的普遍关注。目前,聚合物太阳能电池的能量转换效率已达到7.73%,但离实际应用还有一定的距离。制约电池性能的重要因素是共轭聚合物的吸收光谱与太阳光谱不相匹配以及其载流子迁移率低。合成新的窄带隙聚合物材料对于改善聚合物太阳能电池对近红外区太阳光的吸收,从而提高聚合物太阳能电池的能量转换效率有重要意义。无机纳米半导体材料具有迁移率高、化学稳定性好等优点,如果在聚合物太阳能电池中引入无机半导体纳米晶(如ZnO, CdS, CdSe, TiO2等),将会有利于电荷的分离和传输,从而提高器件的性能。本论文着重为解决上述两个问题而展开研究工作。论文的第一章综述了聚合物光伏材料及其在光电器件应用方面的研究进展。论文第二章采用Stille偶联的方法,以4H-环戊[2,1-b:3,4-b’]双噻吩为给电子单元,将其与四种吸电子单元——4,7-二溴-2,1,3-苯并噻二唑、4,7-二溴-2,1,3-苯并噁二唑、4,7-二溴-2,1,3-苯并硒二唑和1,7-二溴-N,N’-双(2-乙基已基)-3,4,9,10-花酰亚胺共聚,合成出3种窄带隙聚合物光伏材料(P1,P3和P4)。三种聚合物的最大吸收峰位于680-750 nm,光学带隙在1.3-1.5 eV之间,热分解温度大于200℃,有潜力成为聚合物太阳能电池的光活性层材料。基于环戊双噻吩的窄带隙聚合物合成较为困难,论文第三章以双噻吩吡咯为给电子单元,以3,6-二溴-苯酰亚胺、二苯基吡咯并吡咯二酮和2,5-二溴噻吩-3-甲酸已酯为吸电子单元,采用Stille偶联反应,合成了基于双噻吩吡咯的三种新型共轭聚合物(P6,P7和P8)。这三种聚合物的光学带隙在1.6-2.0 eV之间,HOMO(最高占据轨道)能级位于-5.4--5.1 eV,热重分析显示三种聚合物也具有良好的热稳定性,表明三种聚合物都可作为光伏材料应用于聚合物太阳能电池的研究。论文第四章,我们对基于以上六种聚合物的光伏器件进行了研究,其中将5种聚合物(P3-P8)与1-(3-甲氧基羰基)丙基-1-苯基[6,6]C61 (PCBM)共混,制备了5种本体异质结光伏器件,其中基于P7/PCBM的器件效率最高,达到了1.22%。论文第五章将Zn0和CdS纳米晶分别与聚合物复合,制备了PCPDTBT/ZnO纳米晶和MEH-PPV/CdS纳米晶两种复合材料。通过研究复合前后的荧光变化,确认了给体-受体两相界面间发生了由分子能级差引发的光致电荷转移,并进一步研究了两种复合材料的光伏性能。这些研究结果为探索性能更佳的共轭聚合物/无机纳米晶太阳能电池材料体系提供了重要的参考依据。

【Abstract】 In recent years, polymer solar cells (PSCs) have attracted great attention due to their unique advantages, such as low-cost manufacture process, light weight, and the capability to fabricate flexible large-area devices. Although the best power conversion efficiency (PCE) of PSCs reached 7.73%, it needs to be further improved for commercial applications. The PCE of polymer solar cells is limited by two main factors from a view of materials:one is the mismatching between the spectral response of the photoactive layer and the solar-terrestrial radiation, the other is low mobility of polymers. In order to match solar-terrestrial radiation, the synthesis of novel low band-gap conjugated polymers, which can extend their absorptions to near-infrared region, is crucial for the PCE improvement of PSCs. In addition, the introduction of inorganic semiconductor nanocrystals with high carrier mobility and good chemical stability (such as ZnO, CdS, CdSe, TiO2) may enhance the charge separation and transport within PSCs, thus lead to the improvement of device performance.In Chapter 1, the progresses of polymer photovoltaic materials and their applications in photovoltaic devices are reviewed.In Chapter 2, three low band-gap polymers (PI, P3 and P4) are designed and successfully synthesized via Stille cross-coupling polymerization by choosing 4H-cyclopenta[2,1-b:3,4-b’]dithiophene as electron-donating unit and four compounds,4,7-dibromo-2,1,3-benzothiadiazole,4,7-dibromo-2,1,3-benzoxadiazole, 4,7-dibromo-2,1,3-benzoselenadiazole and N,N’-bis(2-ethylhexyl)-3,4,9,10-perylene diimide, as electron-withdrawing units. These copolymers exhibit broad absorption extending into the near-infrared region with the absorption maxima at 680-750 nm and the optical band gaps ranging from 1.3 to 1.5 eV. HOMO(Highest Occupied Molecular Orbital)energy levels of the copolymers vary between-5.0 and -5.3 eV whereas the LUMO(Lower Unoccupied Molecular Orbital) energy levels are pinned between -3.7 and -3.4 eV. The combination of extending absorption into the near-infrared region, optimal energy levels, and excellent thermal properties makes this class of low band-gap copolymers promising for photovoltaic applications.Due to the difficulties in synthesizing low band-gap polymers based on 4H-cyclopenta[2,1-b:3,4-b’]dithiophene, in Chapter 3, dithieno[3,2-b:2’,3’-d]pyrrole is used as electron-donating unit to synthesize conjugated polymers alternating dithieno[3,2-b:2’,3’-d]pyrrole and three electron-accepting units, 3,6-dibromophthalimide, 1,4-diketo-3,6-diphenyl pyrrolo[3,4-c]pyrrole and 2,5-dibromothiophene-3- hexyl formate. Optical characterizations reveal that the band-gaps of the obtained three polymers (P6, P7 and P8) are between 1.6 and 2.0 eV. Electrochemical characterizations show that the HOMO energy levels of P6, P7 and P8 are between -5.4 and -5.1 eV. These results indicate that this type of polymer is promising candidate for efficient polymer solar cells, too.The above six polymers, blended with 1-(3-methoxycarbonyl)propyl-l-phenyl-[6,6]-C-61 (PCBM), are used as active layers to prepare bulk heteroj unction polymer solar cells. Their photovoltaic properties are studied, and it is found that the PSC based on P7:PCBM blend exhibits the highest PCE of 1.22%.In Chapter 5, the composites based on poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cy clopenta[2,1-b:3,4-b’]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)](PCPDTBT)/ZnO nanocrystals and poly[2-methoxy-5-(2-ethylhexyloxy-p-phenylenevinylene)](ME H-PPV)/CdS nanocrystals have been prepared. Both composites show fluorescence quenching, indicating that the photo-induced charge transfer occurrs due to the energy level offset between the donor and the acceptor. Moreover, the photovoltaic property of the composite based on MEH-PPV/CdS is discussed as well.

  • 【网络出版投稿人】 浙江大学
  • 【网络出版年期】2011年 08期
节点文献中: 

本文链接的文献网络图示:

本文的引文网络