Advances in solvent annealing characterization techniques for organic solar cells

<p indent="0mm">Organic solar cells (OSCs) are considered to be the most promising green energy technology of the 21st century due to their low cost and significant advantages such as their lightweight and tunability. The morphology adjustment and crystallinity of OSCs active layer are related to the performance of the device. Therefore, various post-treatment strategies to optimize morphology and adjust crystallinity have been proposed, such as hot annealing (TA), solvent annealing (SVA), and additives. However, the poor compatibility of additives will affect the device performance. TA and SVA are both popular post-treatment strategies. Thermal annealing is to optimize the surface morphology of the active layer by heating the molecules to provide driving force. Unlike thermal annealing, solvent vapor annealing can penetrate into the membrane to provide free volume for molecular movement, and its advantages such as simple operation and flexible control methods have aroused people’s interest. However, the mechanism by which solvent vapor affects the active layer of OSCs is not well understood, which inhibits the development of SVA. Therefore, we summarize several popular dynamic characterization techniques and devices, including different test techniques such as Raman fluorescence spectroscopy (PL), UV-visible absorption spectroscopy (UV-vis), grazing-incidence wide-angle X-ray scattering (GIWAXS), and grazing-incidence small-angle X-ray scattering (GISAXS). This review allows researchers to gain a comprehensive understanding of the dynamic processes of SVA, potentially improving device performance. Finally, the challenges and future development of SVA characterization techniques in OSCs are briefly reviewed.