纳米管形大碳笼金属富勒烯的合成、结构及其在光伏电池中的应用

The higher endohedral metallofullerenes with shape of nano-tube is a new kind of the metallofullerenes, which is recently discovered, and possesses the special electronic structure. Some members of these new metallofullerenes show the properties so called "magic number". The structures of the electronic levels of the new endohedral metallofullerenes could well match the work function of the electrodes of organic solar cell, which is one of the advantages of the higher metallofullerenes. In this project, we plan to investigate the origin of the properties of "magic number", and reveal the special mechanism of their formation. The proposed studies are based on our previous discoveries and determinations of two typical higher metallofullerenes with shape of nano-tube, that is, La2@C100, and Sm2C104. One purpose of this project is to develop a method efficiently producing these new higher metallofullerenes. The three dimensional structures of the as-synthetic samples of the higher metallofullerenes will be determined using the synchrotron X-ray single crystal analysis, and physical properties will be characterized using the several spectroscopic method. We plan to synthesize the derivatives of the higher metallofullerenes, so-called PMBM, and characterize their chemical structures, photo absorptions, and electronic levels. We will further prepare a simple bulk-heterojunction organic solar cell using the P3HT as donor and the PMBM as accepter, and test the performance of as-prepared cell. The advantages using the PMBM as accepter could be found through the comparison with the PCBM and PC70BM as the accepter under the same conditions. We will optimize the parameters of the preparation of the solar cell, and then control the morphology and micro-structure of the photo-electronic active layer, and finally promote the photoelectric conversion efficiency on the basis of the derivates of the as-synthetic higher metallofullerenes.

纳米管状大碳笼金属富勒烯是最近发现的一类结构独特的新型金属富勒烯。它的一些成员具有"魔数"的性质，它的电子能级结构具有与有机太阳能电池电极材料功函数较好匹配的优点。本项目拟在我们发现和确定了两种纳米管状金属富勒烯La2C100和Sm2C104的基础上，进一步探索大碳笼金属富勒烯的"魔数"性质，揭示其特殊的生成机理，进而发展出针对它们的优化的合在方法。利用同步辐射X-射线单晶衍射技术确定其结构，利用多种谱学表征手段测试其性质。合成纳米管形大碳笼的衍生物PMBM，表征其化学结构、光吸收行为以及电子能级结构。利用该衍生物与电子给体材料P3HT结合，组装出原型体异质结有机太阳电池，并与PCBM和PC70BM组装的电池性能进行对比研究，揭示纳米形大碳笼金属富勒烯用作电子接受材料的特色。通过控制制备条件，考察光电活性层的形貌与结构，从而制备出较为有序的微结构，提高电池的光电转换效率。

金属富勒烯作为金属或金属原子簇内嵌于富勒烯碳笼之内形成的一类新型碳与金属杂化的材料，结构非常独特，在诸多方面显示了非常大的应用潜力。相比于C60和C70等空心富勒烯，金属富勒烯的能隙结构更容易与电子给体高分子材料的能级相匹配，减少太阳能电池电荷转移过程中的能量损失，对于提高太阳能的光电转换效率有重要的意义。本项目利用电弧放电方法进行，合成并分离出含镧、钐、钆大碳笼金属富勒烯，进行了质谱、紫外-可见-近红外光谱、电化学循环伏安和微分脉冲伏安方法表征。分别利用八乙基卟啉镍和硫代四硫富瓦烯与分离的金属富勒烯异构体自组装生长出单晶，并用同步辐射X-射线单晶衍射方法鉴定多个金属富勒烯结构。对金属富勒烯体系进行了系统的密度泛函理论研究，在几何优化的基础上，计算了体系的能量、HOMO-LUMO能隙、电荷转移、自旋密度以及静电势等。对La2@C100合成具有溶解能力强PMBM衍生物的尝试，并进行了相应的谱学表征。利用La2@C100的PMBM衍生物进行了原型太阳能电池的制备，并进行了初步的电池参数的测定。研究发现，在电弧放电合成方法中，大碳笼金属富勒烯的生成存在“魔数”现象如La2@C100，“魔数”的金属富勒烯应具有特殊的结构。通过理论计算发现经单晶结构鉴定的纳米管形La2@D5(450)-C100同时具优势的热力学和动力学稳定。对Sm@C80与八乙基卟啉镍组装的单晶解析表明，其结构为Sm@C2v(3)-C80。密度泛函理论计算结果表明，金属Sm向碳笼转移2个电子，电子结构可表示为[Sm]2+@[C2v(3)-C80]2-。通过自旋密度分布，发现了这种+2价金属包结于碳笼内部形成的稳定性金属富勒烯原因。双核金属富勒烯Sm2@D2(35)-C88、Sm2@C1(21)-C92、Sm2@D3d(822)-C104电化学研究发现，大碳笼富勒烯的能隙仍保持，突破了随着碳笼的增大，能隙会趋于减少的传统认识。通过对合成的La2@100衍生物的表征和原型电池的制备和参数测定，为金属富勒烯在太阳能电池领域的应用提供了有价值的信息。