Semi-paracrystallinity of conjugated polymers Jesika Asatryan, Jaime Martín Pérez Campus Industrial de Ferrol, CITENI, Spain
The importance of solar cells in the implementation of renewable energy sources is indisputable. As a promising alternative of silicon based solar cells, organic photovoltaics (OPVs) have emerged, which have advantages over the previous ones, such as being transparent, easy to process and more economical. Organic electronic devices are based on the management of electrical charge carriers by an organic semiconducting material, which is often a conjugated polymer. This ability to manipulate electrical charges is closely related to the solid state microstructure of the polymer as it is known that the transport of charges probably depends on the presence of domains with ordered molecular packing. Consequently, precise control of electrical/electronic properties in semiconducting polymers (and therefore their devices) can only be achieved if their internal microstructure is fully understood and controlled. Recently, however, the scientific community has found that traditional structural models, developed to explain the microstructure of polymeric materials (i.e., amorphous, semi-crystalline and paracrystalline organization), are not able to adequately explain the microstructure of the most advanced semiconducting polymers. Aware of this important problem, our group has endeavored to seek understanding of the structure of semiconducting polymers and has recently demonstrated that these polymers require a new structural model, not contemplated in the traditional list of structural models for polymers. Thus, at the end of 2021 we have presented the semi- paracrystalline model. [1] Here we present the model based on the results of efficient copolymer donor D18 which presents PCE of a 18.22% (certified 17.6%), the highest OPV to date. The support the hypothesis, the solid state transitions of the D18 have been analyzed by Flash-DSC. Then, to understand the solid state microstructure of the polymer and it’s evolution with the temperature, GIWAXS experiments has been done and the parameters of the semi- paracrystallinity have been evaluated. Finally, we present results of PLOM and UV-VIS studies. This work gives us the fundamental information about D18 and enables us to find the link between processing-structure-function relationship of this semiconducting polymer. References 1. Marina, S.; Gutierrez-Fernandez, E.; Gutierrez, J.; Gobbi, M.; Ramos, N.; Solano, E.; Rech, J.; You, W.; Hueso, L.; Tercjak, A.; Ade, H.; Martin, J. “Semi-paracrystallinity in semi-conducting polymers.” DOI https://doi.org/10.1039/D1MH01349A
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