集成高效光俘获结构的柔性有机太阳能电池研究

Flexible organic solar cells (OSCs) have been attracting considerable interest as one of the promising photovoltaic technologies for charming applications in portable intelligent electronics because of their potential in realizing low-cost mass production of large-area, lightweight, and mechanically flexible solar panels via roll-to-roll printing techniques. Regardless of recent advances in highly efficient OSCs, further development on efficiency and lifetime is important theoretical and technological challenges for them to be commercially viable. It is urgent to replace ITO with novel flexible transparent electrodes that have the improved electrical/optical properties, and to design new device structures for further enhancement on the power conversion efficiency. Among those potential methods, the light trapping scheme is indispensable to enable sufficient absorption of incident light in the organic photoactive layer for photocurrent generation. In this proposed project, we will develop high-efficiency flexible OSCs with powerful light trapping structures and metal/dielectric composite flexible electrodes. The project covers device physics, organic/electrode interfacial engineering, and process integration. Primary emphasis will focus on realization of large-area, broadband absorption enhancement in light trapping-structured OSCs. The immersion interference lithography (IL), nanoimprint lithography and numerical simulation with finite-difference time-domain (FDTD) will be utilized to optimize various parameters in OSCs. Light trapping and its effects on efficiency of flexible OSCs will be investigated in the proposed research project. The targeted flexible OSCs will be optimized with a power efficiency efficiency of 15%. We expect this project will provide not only a comprehensive research in flexible OSCs using light trapping structures, but also a new degree of freedom in device design and fabrication.

柔性有机太阳能电池具有卷对卷印刷、可任意弯折、轻便超薄等独特优势，在便携式电子设备等方面潜在应用广泛，但综合性能距实际应用还有较大差距，迫切需要在新型柔性透明电极、高效光电转换方面开拓思路，发展新型器件结构并进行系统研究。采用光俘获结构增加器件活性层的光吸收效率是实现高效有机太阳能电池的重要途径之一。本项目将以集成光俘获纳米结构的新型金属/介质柔性透明电极为切入点，发展适应于宽光谱响应的界面光学调控新方法，结合浸没干涉光刻、纳米压印、仿真计算等实验与理论方法，探索大尺寸、高精度的光俘获微纳调控结构制作工艺，阐明光俘获纳米结构界面的微观形成机制及其与光电转换调控的构效关系，获得基于光俘获结构的高效率柔性有机太阳能电池，器件效率达到15%。力争在深入理解有机太阳能电池的微纳结构光学调控机制，以及柔性器件结构和制备工艺等关键科学与技术问题上有所突破，形成具有自主知识产权的研究成果。

柔性有机太阳能电池因其可弯折、溶液法大面积制备、易携带等特殊优势，在便携设备于电子皮肤等应用场景下有着广泛的使用前景，但是其光电性能、耐弯折性能与大规模制备距离商业化应用还有很长的路要走。制备集成光俘获结构的柔性器件是实现高性能有机太阳能电池的重要方式。本项目团队基于前期工作研究基础，进一步发展和完善光俘获微纳结构，总结了有机太阳能电池中的光俘获策略和柔性电极的构建方案，归纳了衍射、散射、渐变折射率、局域等离子共振、微腔和表面等离子激元等现象的诱发机理及其对器件光俘获的影响机制，并探讨了微纳结构和柔性电极加工工艺的优势与不足，实现了基底层的光俘获机构复制和转移至有机太阳能电池的各功能层的目标，最终实现了其外量子效率、功率转换效率、短路电流、开路电压等关键性能指标的提升。通过研究有机太阳能电池的材料体系，根据不同的能级结构与界面接触情况，应用不同的功能层和柔性电极策略，制备不同结构的高性能柔性有机太阳能电池，在国际上处于领先地位。在使用合适的活性层体系的柔性有机太阳能电池使用热纳米压印技术在银纳米线上引入了可以作为表面等离子激元辐射阻尼通道的分布式侧芽，使得原本通过发热损耗的能量被利用起来，柔性电极的透射率的宽带增加，在480 nm处获得了91.25%的最高透射率，最高光电转换效率为18.12%，超过预期目标。在本项目的资助下，在包括Advanced Materials, ACS Nano, Advanced Function Materials等国际知名期刊共发表SCI论文27篇；申请中国发明专利9项，其中已授权4项，且1项实现技术转让。这些研究成果引起了国际同行科学家的广泛关注和肯定，多篇论文被Wiley集团的Materials Views网站亮点专题报道。项目实施期间，共培养了研究生12名，其中硕士研究生9名，博士研究生3名。