纳米晶组装体的调控及其有机光伏电池研究

The electron acceptor in the active layer of organic photovoltaic cells plays an important role on the conversion efficiency. Inorganic nanocrystals are considered as an ideal electron acceptor of organic photovoltaic cells because of the excellent electron mobility. However, the electron mobility between individual nanocrystals is extremely low and nanocrystals are unlikely to form continuous paths for charge transportation due to the aggregation, which prohibit them being widely employed in the field of high efficiency photovoltaic cells. In this project, nanocrystal assemblies are utilized to replace conventional nanocrystal particles as electron acceptor in high efficiency organic photovoltaic cells. The controllable synthesis of different nanostructured nanocrystal assembly is going to be realized through the investigation on the mechanism of nanocrystal aeembly formation, and the conversion efficiency of photovoltaic cells is able to be improved by accelerating electron mobility in nanocrystal assembly through the strong electron coupling, enlarging the surface area for charge separation, and ensuring the formation of continuous path for carriers transportation. The correlation between properties of organic photovoltaic cells with the nanostructures, components and dispersions of nanocrystal assembly will be analyzed in detail in this project as well in order to lay experimental and theoretical foundations for the design and manufacture of high efficiency organic photovoltaic cells based on nanocrystal in the future.

有机光伏电池激活层的电子受体对电池的效率起着至关重要的作用。无机纳米晶因具有更高的载流子迁移率而被认为是光伏电池中理想的电子受体材料。但由于纳米晶之间电子传输率极低，且易团聚不利于形成连续的电子传输网络，极大的限制了其在高效光伏电池中的广泛应用。本项目利用特殊微观形貌的纳米晶组装体取代传统的纳米晶颗粒，作为电子受体应用于高效率有机光伏电池。重点研究纳米晶自组装的形成机理，实现特殊微观形貌纳米晶组装体的可控制备，通过纳米晶组装体的相互电子作用，提高电子在纳米晶中的迁移速率，增大给体/受体界面面积同时形成连续的电荷传输网络路径，从而显著提高光伏电池的转换效率，分析有机光伏电池的各项性能与纳米晶组装体的微观形貌、组成、分散性等因素之间的调控关系，为进一步设计并制备基于纳米晶的高效有机光伏电池奠定实验和理论基础。

2013年1月-2015年12月，本项目研究按计划顺利进行，较好的完成了各年度的任务。通过在水相中以巯基乙酸包覆的CdTe纳米晶为前驱体，通过阳离子交换的方法掺杂Hg元素，制备了CdHgTe近红外三元合金纳米晶，同时以硬脂酸镉（Cd(SA)2）为镉源化合物和表面稳定剂，硒粉为硒源化合物，十八烯（1-ODE）为反应介质，合成出了具有窄尺寸分布的CdSe纳米晶，并在温度急剧降低的条件下制备了一种碗状CdSe组装体。所制备的CdHgTe 三元合金纳米晶相比于CdTe纳米晶，其粒径大小和晶体结构没有改变，但是荧光性质却因为Hg元素的加入而发生变化，随着Hg元素含量提高，吸收峰发生红移，可根据Hg元素含量的不同，使纳米晶的发射峰在578 nm-887 nm之间进行调节。利用静电吸附等方法，以表面修饰正电高分子的碳纳米管或者导电高聚物P3HT为基体通过自组装作用形成相应的纳米晶复合材料，研究了该复合材料的光响应性质。结果表明，在光照射下，复合材料内部发生了有效的电荷分离， 产生明显的、 稳定的光电流信号，优异的光响应性能说明这种组装体在光伏器件领域有广阔的应用前景。