Researchers Stephanie Amos, Neno Fuller, Wai-Lun Chan, and Hartwin Peelaers from the University of Kansas have published a study in the journal Advanced Energy Materials that sheds light on how organic semiconductors can be designed to improve the performance of organic photovoltaic devices.
Organic semiconductors are appealing for use in electronic devices due to their low cost and flexibility. In particular, heterostructures—layers of different organic materials—with a specific type of energy alignment, known as type-II band alignment, can efficiently separate charges generated by light. This process is crucial for converting sunlight into electricity in solar cells.
The researchers focused on interfaces formed by zinc phthalocyanine (ZnPc) and its fluorinated derivatives (F8ZnPc and F16ZnPc). Using computer simulations and experimental techniques, they found that these interfaces not only have the desired type-II band alignment but also exhibit band bending. Band bending refers to the curvature of the energy levels near the interface, which creates a strong driving force for separating positive and negative charges. This separation is essential for generating electricity in solar cells.
The team used ultraviolet photoemission spectroscopy to confirm the predicted band bending. They also observed that the arrangement of molecules affects the shape of their electronic states. When molecules are stacked vertically, their electronic states resemble those of particles in a box, but this shape is lost when the molecules are staggered.
This research provides valuable insights into how interface-induced band bending can enhance charge separation in all-organic heterostructures. The findings suggest a design pathway for improving the performance of organic photovoltaic devices, which could lead to more efficient and cost-effective solar cells. The study was published in Advanced Energy Materials.
This article is based on research available at arXiv.