异质结纳米晶不仅可保留单个组成部分的性质，同时各部分之间存在的有效耦合作用可赋予它们多种优异的物理和化学特性。Au和Cu2-xS纳米晶分别在可见光区和近红外光区表现出显著的局域表面等离子体共振效应（LSPR），二者结合所形成的Au-Cu2-xS异质结纳米晶的光吸收范围不仅覆盖紫外、可见光以及近红外区域，而且与单纯的Au的吸收相比，Au-Cu2-xS在可见光区的吸收峰位置会发生红移。另外Au周围Cu2-xS的存在也会引起等离子体近场强度的增强。因此Au-Cu2-xS的形貌尤其Cu2-xS对于异质结纳米晶性质的影响很大。探索更简单的合成方法从而实现对Au-Cu2-xS异质结纳米晶的形貌调控，有利于我们从根本上理解耦合的局域表面等离子体共振效应并为拓宽Au-Cu2-xS异质结纳米晶的应用领域提供可能。目前具有这种耦合等离子体效应的Au-Cu2-xS异质结纳米晶已被成功应用在光催化和光热治疗上。 体异质结聚合物太阳能电池作为一种重要的新型太阳能电池，具有成本低、可溶液加工等一系列的优点。在聚合物太阳能电池中掺杂Au或Ag等金属纳米晶，能够提高活性层的光捕获能力，在一定程度上促进器件的电荷分离和电荷传输能力，进而提升器件的整体性能。纯的Au或Ag纳米晶的等离子体共振吸收范围只限于可见光区，虽然可以通过改变纳米晶的尺寸和形状等参数来调节局域表面等离子体共振光谱位置，但是金属纳米晶的等离激元吸收很难覆盖较宽的波谱范围。本论文中制备的金属-半导体型Au-Cu2-xS异质结纳米晶的吸收波谱覆盖紫外、可见光以及近红外区域，掺杂后可实现活性层光吸收的宽带增强。本论文具体内容围绕纳米晶的制备、形貌调控及其在聚合物太阳能电池上的应用展开，主要包括以下三个方面： （1）Au-Cu2-xS异质结纳米晶的形貌控制：我们利用简单的种子生长法制备了Au-Cu2-xS异质结纳米晶，同时通过调控Cu2-xS在Au纳米晶上的原位晶体生长过程，实现了异质结纳米晶中Cu2-xS半导体部分的形貌可控，最终获得了两种形貌的Au-Cu2-xS异质结纳米晶：“Au-多面体Cu2-xS”和“羽毛球”型Au-Cu2-xS。对Au-Cu2-xS异质结纳米晶的光学性质进行了表征，观察到耦合的局域表面等离子体共振吸收特性。与Au或Cu2-xS纳米晶相比，Au-Cu2-xS异质结纳米晶的光吸收范围变宽，与活性层材料的光谱范围更加匹配，因此Au-Cu2-xS异质结纳米晶可显著提升聚合物太阳能电池的光电转换效率。 （2）聚合物太阳能电池的光电性能测试及活性层光吸收宽带增强的机理研究：我们利用具有耦合局域表面等离子体共振效应的Au-Cu2-xS异质结纳米晶提高活性层的光捕获能力。将少量的Au-Cu2-xS纳米晶掺杂在聚合物太阳能电池的活性层中，能够使活性层的光吸收在整个波长范围内增强。模拟和实验结果显示，Au-Cu2-xS纳米晶具有局域场增强以及宽带散射特性，显著地提高了电池的光电转换效率。本文证明了Au-Cu2-xS纳米晶是一种高效的等离子体纳米材料，为解决聚合物太阳能电池光吸收与电荷传输二者很难兼顾的问题（在不增加薄膜厚度的情况下去提高活性层光吸收能力）提供了一种重要的研究思路。 （3）不同类型异质结纳米晶的制备：基于上述制备的Au-Cu2-xS异质结纳米晶及其应用，我们发现异质结纳米晶能够比单一纳米晶具有更多优异的特性。借鉴Au-Cu2-xS纳米晶制备的经验，尝试其它类似异质结纳米晶的制备，进一步证实该合成方法的通用性，丰富金属-半导体异质结纳米晶材料体系。我们主要制备了Au-Cu2-xSe、Ag-Cu2-xS及Au-Cu(Ag)xS三种异质结纳米晶。除此之外，我们还研究了无机盐的存在对Cu2-xS纳米晶形貌和大小的影响，不仅对背后的机理有了更进一步的理解，而且为其他半导体纳米材料的控制合成提供了研究思路。

Hybrid nanocrystals not only retain the properties of individual constituents, but also exhibit many excellent physical and chemical properties endowed by the effective coupling between the various moieties. Au and Cu2-xS nanocrystals exhibit distinct localized surface plasmon resonance (LSPR) absorption in the visible and near-infrared regions, respectively. Hybrid Au-Cu2-xS nanocrystals comparatively display LSPR absorption in a broad range covering ultraviolet, visible, and near-infrared regions. Compared to single Au nanocrystal, Au-Cu2-xS nanocrystals show a red-shifted LSPR absorption peak. In addition, the presence of Cu2-xS around Au can enhance the intensity of plasmonic near-field. Therefore, the morphology of Au-Cu2-xS, especially Cu2-xS, has a great influence on the properties of hybrid nanocrystals. In order to achieve the morphology control of hybrid Au-Cu2-xS nanocrystals, a simple synthesis method is highly deisired, which is not only beneficial to fundamentally understand the coupled LSPR effect but also offers a possibility to expand the scope of application of Au-Cu2-xS nanocrystals. At present, the hybrid Au-Cu2-xS nanocrystals have been successfully applied as photocatalyst and photothermal therapy agent based on the coupled LSPR effect. Bulk heterojunction polymer solar cells (PSCs) have a series of advantages such as low cost and solution processing. Doping metal nanocrystals of Au or Ag etc. in PSCs could enhance the light-trapping in the active layer and promote the charge separation and transport that improving the overall performance of the devices. Although the position of LSPR peak can be adjusted by changing the size or shape of pure Au or Ag nanocrystals, the resonant wavelength range is typically narrow, which restricts the light-trapping degree. In comparison, the absorption spectrum of the hybrid Au-Cu2-xS prepared in this dissertation dicpicts a broad absorption covering the ultraviolet, visible and near-infrared regions. To dope Au-Cu2-xS nanocrystals in the PSCs could induce a broadband absorption enhancement of the active layer. This dissertation mainly focuses on the preparation, morphology control of nanocrystals and their application in polymer solar cells, including the following three aspects: (1) Morphology Control of Hybrid Au-Cu2-xS Nanocrystals: We prepared hybrid Au-Cu2-xS nanocrystals by a simple seed mediated growth approach. In the growth process, the morphology of the Cu2-xS moiety in the hybrid nanocrystals was controlled. Finally different shaped Au-Cu2-xS nanocrystals were obtained: Au-Cu2-xS nanocrystals with polyhedron-shaped Cu2-xS and badmintontail-shaped Cu2-xS. The coupled LSPR were observed through the characterization of the optical properties of hybrid Au-Cu2-xS nanocrystals. Compared with single Au or Cu2-xS nanocrystals, the optical absorption of hybrid Au-Cu2-xS nanocrystals is broaden and matches well with the spectral absorption range of the active layer materials. Therefore, hybrid Au-Cu2-xS nanocrystals can significantly improve the power conversion efficiency (PCE) of PSCs. (2) Evaluation of the Performance of PSCs and Study on the Mechanism of Broadband Absorption Enhancement of Active Layer: The hybrid Au-Cu2-xS nanocrystals with coupled LSPR effect were applied to enhance the light trapping ability of PSCs. Doping a small amount of Au-Cu2-xS nanocrystals in the active layer of the PSCs enables the light absorption enhancement over the entire wavelength range. The simulation and experimental results show that the Au-Cu2-xS nanocrystals have local field enhancement and broadband scattering properties, which significantly improve the PCE of the device. This dissertation demonstrates that Au-Cu2-xS nanocrystals can be a highly efficient plasmonic nanomaterial, which also provides an important strategy to improve the light absorption without increasing thickness of the active layer in PSCs. (3) Preparation of Different Types of Hybird Nanocrystals: More hybird metal-Cu2-xA(A=S, Se) nanocrystals were also successfully made referring to the preparation of hybrid Au-Cu2-xS nanocrystals and their applications, which further confirmes the versatility of the synthesis method we used and enriched the hybird metal-semiconductor nanocrystal list. We mainly prepared three kinds of hybird nanocrystals: Au-Cu2-xSe, Ag-Cu2-xS and Au-Cu(Ag)xS. In addition, we also studied the influence of inorganic salts on the morphology and size of Cu2-xS nanocrystals that helps us to better understand the mechanism behind and conduces to develop other semiconductor nanomaterials.