Unraveling the Complex Nanomorphology of Ternary Organic Solar Cells with Multimodal Analytical Transmission Electron Microscopy

摘要： Elucidating the complex materials distribution in the active layers of ternary organic solar cells is one of the greatest challenges in the field of organic photovoltaics. Knowledge of the nanomorphology is key to understanding photophysical processes (e.g. charge separation, adjustment of the recombination mechanism as well as suppression of the radiationless and energetic losses) and thus improving the device performance. Here, we demonstrate for the first time the successful discrimination and spatial mapping of the active layer components of a ternary organic solar cell using analytical transmission electron microscopy. The material distribution of all three organic components was successfully visualized by multimodal imaging using complementary electron energy loss signals. A complete picture of the morphological aspects could be gained by studying the lateral and cross-sectional morphology as well as the morphology evolution as a function of the mixing ratio of the polymers. Finally, a correlation between the morphology, photophysical processes and device performance of the ternary and the reference binary system was achieved, explaining the differences of the power conversion efficiency (PCE) between the two systems.