Direct arylation-derived non-ionic star-shaped oligomeric CIL materials with Dramatically reduced work functions for organic solar cells

Although numerous photoactive layer materials have been explored for organic solar cells (OSCs), the cathode interface layer (CIL) materials still largely lag behind, however. Till now, ionic perylene diimide (PDI) derivatives are one of the most representative conjugated small molecules CIL materials for OSC. In this study, three new non-ionic star-shaped oligomeric CIL materials named , and involving 1,3,5-tribromo-2,4,6-trifluoro-benzene building, cyclopentadithiophene, rhodamine and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile blocks were designed and facilely synthesized atom-economic direct C–H arylation for OSC. In the follow-up study of structure-property correlation, it was found that all three molecules possess the deepened work function (WF). show good electron transport, and are introduced into the PM6:Y6 system to further explore its effect as CIL that, can effectively suppress charge recombination. Among them, has the best effect of reducing the WF, which reduces the WF of the Ag electrode from 4.30 eV to 3.41 eV. Owing to its deepest WF and best alcoholic processability. The -based devices achieve a highest-power conversion efficiency (PCE) of 14.53 %, corresponding to a of 0.85 V, a of 25.17 mA cm, and an FF of 67.21 %. Our work opens up a new direction for non-ionic, non-PDI and non-fused ring star-shaped CIL materials, and thus diversify the CIL materials.