Organic solar cells are thin-film photovoltaic (PV) devices that use organic materials as the active layer to absorb sunlight and generate electricity. Solvent processing is a crucial step in the fabrication of organic solar cells, as the choice of solvent can significantly influence the morphology and properties of the active layer.
In this study, the OIST researchers investigated the effect of different solvent mixtures on the structure and performance of organic solar cells based on a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). They used a combination of experimental techniques, including grazing-incidence small-angle X-ray scattering (GISAXS), atomic force microscopy (AFM), and photoluminescence (PL) spectroscopy, to characterize the morphology and properties of the active layer.
The researchers found that the choice of solvent mixture had a significant impact on the phase separation and crystallinity of the P3HT:PCBM blend. They observed that using a mixture of chlorobenzene and 1,8-diiodooctane (DIO) led to a more pronounced phase separation and higher crystallinity compared to using chlorobenzene alone. This improved morphology resulted in enhanced charge carrier transport and better device performance, leading to a power conversion efficiency (PCE) of over 5%, which is among the highest reported for solution-processed P3HT:PCBM solar cells.
The study highlights the importance of solvent selection in the fabrication of organic solar cells and provides insights into the relationship between solvent-induced morphology and device performance. By controlling the solvent mixture, it is possible to optimize the phase separation and crystallinity of the active layer, leading to improved charge transport and higher power conversion efficiencies in organic solar cells.
"Our findings shed light on the intricate interplay between solvent mixtures, active layer morphology, and device performance in organic solar cells," says Dr. Masaki Taniguchi, the lead author of the study. "This knowledge can be harnessed to design and fabricate high-performance organic solar cells with tailored morphologies, enabling their wider adoption in next-generation photovoltaic technologies."
