Completely Non-Fused-Ring Small Molecules Based on 3,4-Ethylenedioxythiophene Enable Efficient Ternary Organic Solar...

Integrating a third component into organic solar cells (OSCs) was an important strategy for improving their performance. Although 3,4-ethylenedioxythiophene (EDOT) was widely used in organic photovoltaics, it was rarely used to create third-component materials. In this work, four completely non-fused-ring small molecules based on EDOT, namely Ph-HD, Ph-HDF, T-HD, and T-HDF, were reported as the third components. The introduction of EDOT units not only improves molecular planarity through noncovalent conformational locking but also acts as a strong electron-donating unit to enhance intramolecular charge transfer. Introducing Ph-HD or Ph-HDF into the PM6:BTP-eC9 binary system not only enhances light harvesting but also forms a cascading energy level to improve charge transport. The crystallization time of the acceptor was prolonged, and crystallinity was improved with the introduction of the third component, as characterized by in situ UV-Vis absorption spectroscopy and grazing-incidence wide-angle x-ray scattering. The devices of PM6:Ph-HD:BTP-eC9 achieved a power conversion efficiency of 18.44%, higher than the 17.66% of PM6:BTP-eC9. This work provides an effective strategy for constructing high-planarity, completely non-fused-ring small molecules and high-performance ternary organic solar cells.