基于ICT模型的有机光伏电池界面电子结构与光电转换研究

The concept “Interfacial electronic structures at organic heterojunctions and optoelectronic conversion thereof” is one of the key basic research topics to break through the current efficiency limitation. However, its fundamental knowledge remains unclear and has recently attached much attention. In the proposed project, we will focus on electronic structures at donor-acceptor interface and organic-electrode interface obtained by applying the ICT (Integer charge transfer) model to photoelectron spectroscopy and synchrotron radiation in combination with device properties and precision optical spectroscopy, which will enable us to derive the relationship between interface electronic structures and optoelectronic properties in organic solar cells. The project aims to achieve the in-depth understanding about the influence of the ICT caused-electronic structure re-alignment at donor-acceptor interface on the excition dissociation and charge recombination, interfacial ICT states on the energy of the intermediate excited charge transfer states, and the energetics at electrode interface on the real charge injection level into the device during operation. As per the characteristics of the interface obtained in the project, it is able to achieve the high performance organic interface by choosing the materials with different ICT energies. The research will provide a novel guidance for interface engineering, high-efficiency organic solar cells and the material designs.

“有机半导体界面电子结构与光电转换”是突破当前有机光伏电池效率瓶颈的关键基础科学问题之一，然而对它的认识并不清晰，相关研究是当今有机电子领域的前沿。本项目以有机光伏电池给体-受体界面、有机半导体-电极界面为研究对象，研究方法上综合采用光电子能谱、同步辐射、结合ICT(Integer charge transfer)模型进行界面电子结构表征与分析，并辅以器件性能与精密光谱等，围绕界面电子结构与光电转换机制，重点探索基于ICT模型的给体-受体界面电子结构重排对激子分离、复合行为的影响规律;界面ICT态对激子电荷转移中间态能量的影响;深入理解在器件工作中电极界面电子结构与载流子真正的提取注入能级之间的内涵。凝练界面特性，实现通过选用具有不同ICT能量的有机半导体获取高性能界面的目标。该研究为界面调控、实现更高效率的有机光伏器件与有机半导体材料设计提供依据，具有重要科学和应用意义。

有机光伏电池是实现新型高效光伏电池的重要突破口，引起了广泛的关注。目前，对其关键界面电子结构、光电转换等界面物性的认识并不清晰，制约了有机半导体材料与器件开发向更高层次的发展。本项目基于ICT模型，对有机光伏电池给体-受体界面，有机半导体-电极界面的电子结构与光电转换开展了深入研究，取得了一系列研究成果，具体包括：（1）构建了有机光伏电池给体-受体三种界面电子结构完整的模型，结合器件性能，揭示了界面电子结构对激子分离、开路电压损失的影响机制；（2）构建了N型掺杂有机半导体-电极界面统一的界面电子结构，实现了掺杂对电极界面更具规律性调控；（3）考察了器件制备和工作中，氧气对有机半导体-电极界面能级排布的变化，探讨了对载流子注入效率的影响；（4）在界面电子结构研究基础上，调控给体-受体界面，促进激子分离，调控电极界面，实现了3.6 eV极低的阴极功函数，构建了优异的欧姆接触，显著提高了有机光伏电池的效率。本项目取得了预期的研究成果，揭示了多种界面物性，并且发展了若干界面调控的方法，为实现高性能有机光伏器件提供了理论指导和技术借鉴。