Isomeric Effect in Unidirectionally Extended Fused-Ring Electron Acceptors

We designed and synthesized two isomers AOIC1 and AOIC2 by unidirectional extension of the same asymmetric precursor in different directions and separated by selectivity of Lewis-acid-mediated Friedel-Crafts reaction due to different steric hindrance of the side chains. AOIC1 and AOIC2 were compared with our reported AOIC to study the isomeric effect. The only difference in three isomers is isomeric fused-ring cores. The AOIC series exhibit different molecular stacking in single crystals and dipole moments. From AOIC to AOIC1 and AOIC2, hypsochromic optical absorption, similar lowest unoccupied molecular orbital, down-shifted highest occupied molecular orbital, and decreased electron mobility are presented. Organic photovoltaic cells were constructed using the AOIC series as acceptors and wide-bandgap J71, medium-bandgap PM6, and narrow-bandgap PTB7-Th as donors. Combinations of AOIC and PTB7-Th with relatively narrower bandgaps as well as of AOIC1/AOIC2 and J71/PM6 with relatively broader bandgaps yielded higher device efficiencies.

Automated summary

Two isomers, AOIC1 and AOIC2, were designed and synthesized from a common asymmetric precursor, showing differences in optoelectronic properties in photovoltaic devices. Combining narrow-bandgap AOIC1/AOIC2 with wide-bandgap J71/PM6 resulted in higher device efficiencies.