Understanding The Crystalline and Amorphous Morphology of Organic Solar Cells using Grazing-Incidence X-Ray and Neutron Scattering Techniques

Organic photovoltaic molecules or polymers typically form semicrystalline thin films. It is widely recognized that the bulk heterojunction (BHJ) morphology of organic photovoltaic thin films, which consists of both crystalline and amorphous regions, plays a crucial role in determining the performance of devices. However, understanding the intricate three-dimensional multi-length scale morphology of these thin films remains a grand challenge. In this talk, we will present our recent progress on decoding the complex BHJ morphology of OPVs and developing strategies to control the morphology to enhance device performance. In addition to employing conventional techniques like GISAXS/GIWAXS, we will introduce two innovative methods: GTSAXS, which allows for the quantification of vertical nanomorphology, and GISANS combined with deuteration, a technique used to detect amorphous phase structures. Armed with these state-of-the-art scattering techniques, we investigated the optimal active layer morphology for OPVs, aiming at understanding the impacts of amorphous and crystalline phase structures on device performance and to advance the practical applications of these devices. Furthermore, these scattering techniques can also be applied in material science, chemistry, biology and condensed matter physics studies. By modifying the wavelength of the probing beam and the experimental geometry, a variety of sample types, such as solutions, powders, surfaces and thin films, can be studied, covering wide length scales as well as versatile dynamic and kinetic behaviors.