This project will evaluate the aromaticity of stacked dimer structures with potential singlet fission properties via quantum chemical calculations. The ground state of π-stacked dimers, in which two 4nπ antiaromatic molecules are cofacially assembled at a short stacking distance, can display aromatic character, a phenomenon termed stacked-ring aromaticity. Molecular systems exhibiting stacked-ring aromaticity have attracted specific attention for their excited-state properties, especially in the context of potential singlet fission (SF). For those with suitable S1 and T1 energies, the excitation of stacked dimer may localize on just one of the 4nπ-electron monomers which interacts with the other to initiate the SF process. Several 4nπ-electron stacked systems will be evaluated during the project by multiple aromaticity indices (NICS, ACID, MCI, EDDB, etc.) and TDDFT. Through these calculations, we plan to reveal the interplay between stacked-ring aromaticity and singlet fission properties.