Based on novel organic semiconductors, organic solar cells are an interesting alternative to conventional silicon based solar cells as they feature new possibilities. Using wet chemical processing, they can be manufactured with large-scale production methods such as roll-to-roll printing. Consequently, the production of organic solar cells has the potential to become very cheap and easy. With in-situ grazing incidence small- and wide-angle X-ray scattering (GISAXS and GIWAXS) studies, we gain information on the kinetics of inner interface structures of the respective electrodes, blocking layers and active layers of the solar cells during processing.<br/>In terms of large-scale usability, one of the major challenges for organic solar cells is to overcome their relatively short lifetime, as compared to their inorganic counterparts. To gain a deeper understanding of organic solar cell degradation with respect to changes in the active layer nano-morphology, we present in-situ studies on model donor-acceptor organic semiconductor based solar cells during the first hours of operation. The in-operando studies reveal information on both, its evolving current-voltage characteristics and the active layer nano-morphology. For that purpose, GISAXS / GIWAXS measurements and current-voltage (IV) tracking of the operating solar cell are performed simultaneously to gain fundamental understanding. Starting from an optimized morphology of the active layers in terms of highest efficiencies for organic solar cells, depending on the donor-acceptor organic semiconductor system, a mixing or demixing process are identified to cause transformations of the inner interface structure. The altered morphology is less optimal for charge transport through the active layer due to poor percolation in a too fine morphology or poor splitting of excitons in a too coarse morphology.

Probing interface transformations in organic solar cells with in-situ and in-operando scattering studies

ACS Spring Meeting 2021

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