HEFOS – High Electric Fields at Organic Semiconductor Heterojunction Interfaces

在有机半导体领域中，电荷载流子在第二类异质结中的转移已经获得了巨大的吸引力。界面处的相关电荷转移态不仅负责有机太阳能电池中的复合过程，其中它们限定开路电压和电荷产生，而且它们还被用于所谓的“激基复合物”发光二极管中以产生具有合理效率的光。此外，穿过异质结界面的电荷可以吸收光。虽然这一过程的横截面相对较低，但最近的出版物表明，通过与微腔的结合，入射光的主要部分被吸收，从而产生新一代的NIR光电探测器。分子间系统可能受到外部电场的影响更强，例如，与分子内复合和吸收过程相反。通过这种方式，很可能可以从外部调整界面过渡的属性。本项目的目的是设计出将高电场施加到施主和受主材料界面的器件结构，以调节发射和吸收的光谱范围。此外，将感兴趣的是详细说明在这种界面处的强电荷积累下的操作，这对于潜在的高激发实验和应用（例如电驱动激光器）是重要的。我设想通过与几个外部合作伙伴合作来澄清潜在的物理学，这些合作伙伴将带来他们的专业知识和知识。

The transfer of charge carriers at heterojunctions of type II has gained an enormous attraction in the field of organic semiconductors. Related charge-transfer states at the interface are not only responsible for recombination processes in organic solar cells where they define the open circuit voltage and the charge generation but they have also been employed in so-called "exciplex" light-emiting diodes to create light with reasonable efficiency. Further, charges traversing the hetorojunction interface can absorb light. Although the cross-section for this process is relatively low, recent publications reveal that by combination with a micro-cavity, a major part of the incident light is absorbed, leading to a new generation of NIR photodetectors.Intermolecular systems can potentially be affected much stronger by an external electrical field, e.g. in contrast to intramolecular recombination and absorption processes. By that, it is likely that the properties of the interface transitions can be tuned externally. It is the aim of this project to work out device structures to apply high electric fields to the interfaces of donor and acceptor materials in order to tune the spectral range of emission and absorption. Further, it will be of interest to elaborate the operation at strong charge accumulation at such interfaces which is important for potential high excitation experiments and applications, such as an electrically driven laser. I envision to clarify the underlying physics by cooperating with several external partners who will bring in their expertise and knowledge.