有机太阳电池纳米随机织构复合电极的陷光机理、结构设计与实验研究

Organic solar cells (OSCs) have attracted intensive attention because of their advantages of flexibility, light weight, and potential for low cost. However, due to the low carrier mobility of organic semiconductor materials, the absorption layer thickness of OSCs is subject to the restriction for the increased recombination probability of photogenerated carriers. OSCs with the limited thickness of the absorption layer readily suffer from the insufficient light absorption and low efficiency. The introduction of light-trapping structure into OSC can allow to fully absorb light without increasing the absorption layer thickness, while to reduce the recombination probability of photogenerated charge carriers.Whereas,until now,no obvious efficiency improvement has been found for OCSs based on periodic light- trapping structure.More intensive research should be carried out on structure design, spectral response and interface recombination for light-trapping effect. In this project, we propose a new method to improve the light absorption efficiency of OSCs with the combination of scattering of the incident light and diffuse reflection of the transmitted light. To realize this purpose, a new structure with random textured front electrode and double layers back textured electrode will be designed for OSCs and the prototype devices will be fabricated. We will focus on revealing the mechanism of light-trapping effect of this structure and find an effective way to manage the light absorption for OSCs. From the point of device realization view, we will adjust the preparation process of light-trapping electrode to be compatible with the existing organic process. At the same time, by interface modification and electrode optimization, we will ensure that the light-trapping structures of the electrodes not only improve the light absorption, but also do not affect the photogenerated carrier transport processes. As a result, overall performance improvement of OSC can be achieved. Finally, through theoretical analysis and experimental study, we will establish a firm foundation for the further improving of the light absorption and conversion efficiency of OSC based on the light management.

有机太阳电池吸收层载流子迁移率低，使电荷复合几率随吸收层厚度增加，制约了器件光电转换效率的提升。引入陷光机制可以实现超薄吸收层对光的充分吸收，是改善载流子复合、提高效率的重要手段。然而现有的周期性陷光结构难以使电池的整体性能得到改善，在结构设计、光谱响应、界面复合等方面有待进一步深入的研究。本项目提出一种具有随机织构绒面前电极、漫反射结合光学隔离层复合背电极的三重光吸收增益效果的光管理方案。采用纳米形貌微调控、界面修饰、多层膜光学参数匹配等手段，实现对入射短波光的前散射、长波光的背漫反射以及吸收层的光强分布调控，获得宽谱域光吸收增强效果。通过三维光学理论模拟，揭示随机织构陷光电极提高有机太阳电池光吸收效率的机理。本项目兼顾电极的陷光结构在光学和电学上对电池的双重影响机制，最终制备出基于新型的前散射、背漫反射及光强增强相结合的有机电池原型器件，为进一步提高有机电池的光吸收和转换效率奠定基础。

国家自然科学基金面上项目“有机太阳电池纳米随机织构复合电极的陷光机理、结构设计与实验研究”（编号：61377031）。引入陷光机制可以实现超薄吸收层对光的充分吸收，是改善载流子复合、提高效率的重要手段。提出一种具有随机织构绒面前电极、漫反射结合光学隔离层复合背电极的三重光吸收增益效果的光管理方案，获得宽谱域光吸收增强效果。.研究的主要内容包括：（1）薄膜太阳电池绒面散射陷光结构的模拟计算。（2）倒结构聚合物太阳电池中绒面ZnO、AZO电子传输层的优化设计；聚合物太阳电池FTO前电极的绒面陷光结构设计；宽光谱散射Ag纳米线/ZnO复合电极的结构设计。（3）PTB7-Th:PCDTBT:PC70BM三元体系聚合物太阳电池的构建，以及阴极界面修饰层的研究。.取得的主要研究成果为：（1）开发了一套完整的绒面散射建模方法，即基于Reyleigh-Sommerfeld理论的Matlab数值方法。并针对随机形貌、周期形貌、叠加形貌三种不同形貌散射特性进行了建模分析，发现其散射特性由其内部结构特征尺寸占主导所对应的散射机制来主导。（2）通过溶胶凝胶法制备得到随机陷光的绒面AZO电子传输层；实现了适合聚合物太阳电池FTO前电极的绒面陷光结构设计；构建了宽光谱散射Ag纳米线/ZnO复合电极结构。建立一整套基于电极陷光结构的有机太阳电池器件结构设计体系和工艺方案，阐明各层随机陷光结构对光散射、光增强和光吸收的作用，在实验上实现了基于前散射及光场增强的有机电池原型器件。（3）设计并组建了PTB7-Th:PCDTBT:PC70BM三元体系有机聚合物太阳电池，提出并设计了UVO-ZnO NPs/PFN双阴极界面修饰层，并将其应用于三元体系有机聚合物太阳电池，实现了最高10.87%的器件效率，并且使器件的稳定性得到大幅提升，有力地推动了聚合物太阳电池大规模产业化的进程。