包覆型银纳米结构对有机太阳能电池性能的优化研究

Organic solar cells (OSCs), as a clean and renewable energy, are very important for utilizing solar energy on a large scale and then supplying cheap electric energy. However, the poor efficiency of OSCs limits their application. Therefore, increasing photoelectric convertion efficiency(PCE) of OSCs has attracted a lot of attentions. A great many researches had indicated that noble metallic nanostructures incorporating into OSCs can enhance light absorption of active layer. But this technology also lead to queching of excitons and recombination of free charge carriers at metal/organic interface. These are very disadvantageous for improving the efficiency of OSCs. Therefore, in this project, silver-Teflon AF core-shell nanostructure and MoO3/silver/MoO3 samdwich nanostructure with concave-convex interface will be designed and prepared, and then incorporated into OSCs for avoiding exciton quenching and carrier recombination loss. The ultimate realization of these goals is to improve PCE of OSCs more efficiently. The excitation of surface plasmon polaritons and the near-field enhanced effect of the coated silver nanostructures will be investigated theoretically, and then the physical mechanism will be revealed. The coupling properties between the incidence light field and surface plasmon polaritons in the coated silver nanostructures will be probed. The regulative rules of multi-model surface plasmon polaritons leaded by composite coated silver nanostructures on light absorption of active layer will be established. The influence of the coated silver nanostructures on essential physics processes of OSCs, such as the generation and diffuse of excitons, the separation, transport and collection of charge carriers etc, will be investigated experimentally when they are incorpated into OSCs simultaneouly. The optical and electrical properties of OSCs should be optimized simultaneously. And then the larger improvement of OSCs performances will be expected. These investigations should be applied to develop high performance OSCs.

有机太阳能电池（OSCs）作为一种清洁可再生能源对大规模利用太阳能、提供廉价电能具有重要意义。但OSCs的效率低是制约其应用的关键因素之一。大量研究表明在OSCs中植入贵金属纳米结构有利于提高活性层的光吸收,但该技术在提高OSCs光吸收的同时，也导致了金属界面处载流子的复合损失、激子的淬灭损失，这对OSCs光电转化效率的提高是不利的。为此，本项目提出设计制备聚四氟乙烯包覆的银纳米核-壳结构及三氧化钼包覆的银纳米层状凹凸结构，将其同时植入OSCs中，使OSCs的光、电性能同时得到优化，实现其光电转化效率的显著提高。研究包覆型银纳米结构的表面等离子激元激发及局域场增强的物理机制，研究多模式表面等离子激元激发对活性层光吸收的调控规律；研究包覆型银金属纳米结构及其耦合作用对OSCs中激子的扩散与解离、载流子传输与收集行为的影响规律。本项目研究将为高效率OSCs的研发提供重要的科学依据。

主要研究内容：.（1）研究了包覆型银纳米结构的等离激元共振模式及光子模式的激发机制、耦合效应及其对活性层光吸收的调控规律，实现了电池光吸收效率的有效提高。.（2）研究了金属纳米颗粒引入到有机太阳能电池缓冲层或缓冲层与活性层界面处对电池中激子的产生、扩散与解离、载流子的传输与收集行为的影响，并对其中的物理机制进行了探索。.取得的重要研究结果及其科学意义：. （1）新技术方面：.发展了二氧化硅包覆型银纳米立方体提高电池PCE的新技术；发展了一种将具有大尺寸的二氧化硅包覆型纳米银球镶嵌于阳极缓冲层和活性层之间提高电池PCE的新技术；发展了一种将三种具有互补表面等离激元共振吸收的银纳米颗粒混合植入活性层底部提高电池PCE的新技术；提出了一种利用聚乙烯微球构筑具有随机分布的二维亚波长尺度的凹凸结构提高电池PCE的新技术。. （2）器件新结构设计方面：. 开展了表面等离激元增强电池光吸收的多项理论研究。设计了一系列结构新颖的金属纳米光栅结构，如超小周期和超大高宽比的银纳米墙光栅、介质包覆的梳状金属纳米光栅、介质/金属/介质核壳结构光栅等，引入OSC中，通过同时激发丰富的光子模式（腔模式和布洛赫模式）和表面等离激元共振模式等，实现了高效、宽谱、广角光吸收的提高。.（3）新现象、新机理方面：.发现金属纳米颗粒不仅作为表面等离激元共振基元提高了激子的产生率和解离率，而且作为界面层可改变阳极缓冲层PEDOT:PSS的表面能，进而促进了活性层的垂直相分离，从而提高了载流子的传输和收集效率；发现了二氧化硅包覆层不仅能减少激子的淬灭和载流子的复合损失，还有利于提高光散射，进而提高活性层的光吸收；发现了二氧化硅包覆层改变了银立方纳米颗粒的LSP边共振相位。.上述研究成果丰富了表面等离激元共振理论，对金属纳米结构提高OSC光电转化效率的机理有了全面的认识和理解。本项目研究将为高效OSC的研发提供科学依据和理论指导。