【作者】 白茹；

【导师】 陈红征； 汪茫；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2008， 博士

【摘要】 光电功能器件的性能表现为激发态载流子的产生、解离和传输行为，复合材料的凝聚态结构对其激发态性能有着至关重要的影响。一维纳米有序复合结构增强的光致电荷转移可显著提高载流子的解离和传输效率，因而为优化光电功能器件性能的有效途径之一。通过有机半导体材料纳米薄膜形貌调控和高度有序纳米阵列结构的组装，可以提高半导体材料的载流子传输性能。本研究将有机半导体材料进行纳米级的复合，尤其是采用以无机材料低维结构为模板进行纳米有序复合的方法，增强载流子的分离和定向传输，从而达到光电功能协同增强的目的。本论文对实验制得的酞菁、苝酰亚胺、和C₆₀半导体有序纳米结构及其阵列的光电性能进行了研究，为制备基于酞菁、苝酰亚胺和C₆₀的复合材料的光电子器件提供了数据积累。本文首先综述了光电功能纳米薄膜在有机太阳能电池领域的应用研究，并具体介绍了基于酞菁染料、苝酰亚胺衍生物以及富勒烯C₆₀纳米薄膜有机光伏器件的研究进展。本研究合成并提纯了金属酞菁、三明治型稀土酞菁和吡啶-苝酰亚胺，通过元素分析、紫外可见吸收光谱、红外吸收等手段对合成物质的化学结构及纯度进行表征。DSC-TGA分析表明，合成的酞菁和吡啶-苝酰亚胺分子具有较好的热稳定性。p型半导体材料稀土酞菁在酸性溶液中易被质子化，质子化的分子在外加电场作用下可定向迁移。基于这一现象，通过电泳沉积法在导电ITO玻璃上制得酞菁铒薄膜，并通过调节沉积时间、电场强度和退火处理条件调控酞菁铒薄膜的聚集态结构。实验结果表明，延长沉积时间、提高沉积电压可使酞菁铒以纳米线、微米线结构沉积于基片上，而通过退火处理可制得V型、Y型及花状形态的微米结构。采用紫外-可见吸收光谱与近红外吸收光谱研究了酞菁铒薄膜的光响应性能，发现稀土酞菁薄膜在可见光和近红外区均具有较高的光敏性，表明稀土酞菁可用于制备薄膜型红外探测器。同样，带有杂氮原子的n型半导体材料吡啶-苝酰亚胺亦可被质子化实现电泳沉积。因此，通过分步沉积与在混合溶液中共沉积的方法得到了稀土酞菁／吡啶-苝酰亚胺复合薄膜。通过薄膜形貌和吸收光谱表征发现，稀土酞菁由于含有更多的易质子化氮原子而具有较吡啶-苝酰亚胺更大的沉积速率。Ⅰ-Ⅴ特性曲线表明稀土酞菁／吡啶-苝酰亚胺复合薄膜显示p／n异质结的整流特性。采用高度有序的、具有垂直导电基板平行生长的纳米孔道的多孔阳极氧化铝（AAO）作为模板，通过电泳沉积或真空蒸镀的方法将酞菁铜、酞菁铒和吡啶-苝酰亚胺在模板孔内组装，得到了高度有序、定向生长的有机纳米线阵列结构。纳米线在模板中的生长遵循“bottom-up”生长模式，通过控制沉积时间可得到由底部开始生长的、填充不同程度的纳米线结构。纳米线的直径和长度可通过选用相应孔径和厚度的AAO模板进行调控。采用这一高度有序的吡啶-苝酰亚胺纳米线阵列作为光敏层制备的双层光导体器件具有比本体材料高出一个数量级的光电导。载流子的传输通道与传输方向一致是器件性能优化的主要原因。通过在AAO中电泳沉积得到酞菁纳米线阵列，而后在其表面蒸镀吡啶-苝酰亚胺得到的p／n异质结纳米光电器件表现出光伏特性。这一制备方法为获得有机复合光电功能有序纳米结构提供了一条新的制备思路。C₆₀因其优异的电子传输性能在有机太阳能电池器件中得以广泛应用。用AAO作为模板，通过电泳沉积法将分散在混合溶液中的C₆₀带电聚集体组装于AAO模板内，得到了垂直于导电基底生长的C₆₀纳米阵列。相同的沉积条件下，使用Al和Au两种不同的导电基底分别得到了C₆₀纳米线和纳米管两种不同的阵列结构。此外，本研究首次利用模板表面润湿方法得到了C₆₀纳米线阵列，并对C₆₀纳米线阵列的光导性能进行了研究，发现其光敏性相对于本体薄膜材料提高了一个数量级以上。通过对40、60、80 nm三种不同直径和4、8、10和15μm不同长度的C₆₀纳米线阵列的光导性能对比研究，发现纳米线阵列的光导性能强烈依赖于纳米线的直径和长度，纳米线直径越小、长度越短，纳米线阵列的光电导性能则越好。更多还原

【Abstract】 The performance of optoelectronic functional devices mainly exhibits as the generation, separation of excited charge carriers and the followed transportation of free charge carriers. The aggregation state of organic composite materials plays a vital role in determining the device performance. Photo-induced charge transfer can get enhanced in one dimensional ordered nanocomposites and thus can greatly improve the separation and transportation of charge carriers which are the key factors influencing optoelectronic device performance. The transportation capability of charge carriers in organic semiconductors can be effectively improved through controlling the morphology of organic nano-films and the assembly of highly-ordered organic nanoarrays. The present dissertation focuses on organic semiconductor composite materials at nanometer scale, especially the ordered nanocomposites with the low dimensional inorganic nanostructures as the template, so as to enhance the separation and orientational transportation of charge carriers, and to achieve the co-enhancement of optoelectronic properties. In this work, ordered nanostructures and nanoarrays made from phthalocyanines, perylene-diimide derivative and C₆₀ semiconductors were prepared and their optoelectronic properties were studied, which presents fundamental experimental results for the fabrication of optoelectronic devices based on the phthalocyanines, perylene-diimide derivatives and C₆₀ semiconductors.The recent progress on the application of organic nano-films with optoelectronic functionalities in the area of organic solar cells （OSCs） was reviewed first. A detailed description was covered on organic photovoltaic devices based on phthalocyanine dyes, perylene-diimide derivatives and fullerenes.In this work, metal phthalocyanines, rare earth bisphthalocyanine （REPC2） with sandwich molecular structure and pyridine-perylenediimide （PPD） were synthesized and purified. The chemical structure and purity were characterized by fourier transform infrared spectroscopy, ultra violet-visible （UV-vis） spectroscopy, and elemental analysis. The DSC-TGA analysis indicated good thermal stability for these compounds.The p-type organic semiconductor of phthalocyanines contains bridging nitrogen atoms and can be easily protonated in organic acid solution. The protonated phthalocyanine molecules can orientationally migrate and nucleate on the negative electrode under external electric field. Based on this phenomenon, erbium bisphthalocyanine （HErPc₂） films on indium-tin-oxide （ITO） glass were prepared by electrophoretic deposition （EPD） method. The aggregation structure of the HErPc₂ films could be controlled either by changing the EPD time or EPD voltage or by annealing treatment. Through prolonging EPD time or increasing EPD voltage, the aggregation morphologies of HErPc₂ films on the ITO glass could change from nanowires to microwires. V-type, Y-type or flower-shape HErPc₂ microstructures were formed after annealing treatment of the HErPc₂ films prepared by EPD. The photoresponse of the HErPc₂ films was investigated by UV-vis spectroscopy and near infrared （NIR） spectroscopy. The high photoresponse of the HErPc₂ films was observed in the UV-vis and NIR region, which indicates the potential application of rare-earth biphthalocyanines as OSCs devices and NIR photodetectors. Similarly, PPD films with nanostructures were also prepared by electrophoretic deposition method because the N-atom-bearing PPD molecules can also be protonated in solution.HErPc₂/PPD nanocomposite films were prepared by two-step EPD and electrophoretic co-deposition method. The morphologies and the UV-vis absorption spectra of the composite films indicated that, due to more easily protonized nitrogen, the rare earth bisphthalocyanine molecules exhibited a much faster electrophoretic velocity than the PPD did at the same applied electric field. I-V characteristic curves demonstrated p/n heterojunction rectification for the HErPc2/PPD nanocomposite films.Using highly-ordered porous anodic aluminum oxide （AAO） with nanopores perpendicular to the conductive substrate as the template, highly-ordered and well-aligned organic nanowire arrays were prepared by assembly of CuPc, HErPc₂ and PPD in the AAO templates via EPD and vacuum deposition technique. Further studies revealed that the growth process of the nanowires in the AAO pores followed a "bottom-up" growth model, which enables us to readily control the length of the organic nanowire arrays by varying the deposition time. The highly-ordered organic nanoarrays were free-standing after removing the AAO supports. The length and diameter of the as-prepared organic nanowires could be easily controlled by selecting different pore sizes and film thicknesses of the AAO templates. The photoreceptor with the organic nanowire arrays as charge generation layer （CGL） showed one order of magnitude higher photosensitivity than the photoreceptor with the casting bulk film as CGL. The improved photosensitivity was attributed to the large interfacial area for exciton splitting and orientational nanochannels for charge carrier transportation.HErPc₂/PPD composite with p/n heterojunction nanostructure was prepared by EPD HErPc₂ nanowire arrays in AAO template and followed by the vacuum deposition of PPD on them. The optoelectronic devices based on the HErPc₂/PPD p/n heterojunction nanostructures exhibited photovoltaic properties. Therefore, this mentioned template-based synthesis of organic p/n heterojunction opens up a new approach for the preparation of ordered organic nanostructured composites with optoelectronic functions.C₆₀ is an n-type semiconductor with excellent electron transportation property and thus has been extensively used in OSC devices as the electron-acceptor. By electrophoretic deposition of C₆₀ aggregates from mixed solvent of toluene and acetonitrile into the nanopores of the AAO template, C₆₀ nanoarrays have been successfully prepared. Under the same EPD conditions, C₆₀ nanowire arrays and C₆₀ nanotube arrays were formed by using two different AAO templates with Al conductive substrate and Au conductive substrate, respectively. It is worth to mention that C₆₀ nanowire arrays were prepared by template-surface-wetting method for the first time. The photosensitivity of the photoreceptors with the highly-ordered nanowire arrays as CGL was enhanced by one order of magnitude compared with that of their bulk films. The study on the photosensitivity of photoreceptors made from different C₆₀ nanowire arrays with 40, 60 and 80 nm in diameter and 4, 8, 10 and 15μm in length revealed the high dependence of the photoconductivity on the diameter and the length of the C₆₀ nanowires. This effect of the nanowire size on the photosensitivity should be related to the transportation of the photo-generated carriers in the nanowire arrays. The faster carrier transportation was found in the nanowires with a smaller diameter and a shorter length.更多还原