show a red shifted absorption and an inversion of ratio intensity between its two first absorption bands. This pattern is typical of the H-aggregate formation, which would be a possible explanation for this observation as face-to-face dimers can be seen in the crystal structure of 2a. In thin films, the double-annulated O-doped BACD derivative 6 see its lowest energy band shifting to larger wavelength while its absorption intensity increase compared to the following higher energy absorption band, an observation that could be explained by the formation of Jaggregates. 24 were considered. It resulted in a non-planar structure for 9, with a tilt between the central phenyl moiety and the side part from 40° to up to 120° (Figure and S44). The movement of each side of the molecule is independent from the other one. This flexibility has been considered for the calculation of the optical properties. As already observed in our previous study, the lateral chains were not considered as they do not have an influence on the optical properties and thus compounds 2a and 2b were equivalent for the computational part and denoted as 2. For all compounds, the lateral chains were replaced with a methyl group. The experimental and computed spectra (Figure and Table ) show a good agreement and the differences in terms of blue-or red-shift are also retrieved. For 2 (4), the first absorption band, experimentally at 539 nm (562 nm), corresponds to a HOMO-LUMO transition and is ascribed to a S 0 → S 1 excitation (Table ) at 536 nm (582 nm). Experimentally, for 6 and 9, the area around 400 nm shows an increase of its molar extinction coefficient when compared to 2 and 4, leading to a main absorption band. The experimental transitions at 387 nm and 366 nm for 6 and 9, respectively, are computed at 380 nm and 367 nm respectively (Table ). One can notice that the oscillator strength of 6 and 9 in the 400 nm area are larger than the ones of 2 and 4 in the same area (0.75 and 0.86 for 6 and 9 vs 0.58 and 0.67 for 2 and 4), indicating the same trend as the one observed experimentally. and) some small differences can nevertheless be observed. Depending on the dihedral couple, the molecule is more or less conjugated, and it results in a slight blue-or red-shift of the absorption peaks. The orbitals that are involved in the transitions (Figure and S47) can involve only one side of the molecule or both sides, inducing a large CT character. Thus, depending on the structure, the CT character can vary but is always the largest among the four molecules of this study. Consequently, the optoelectronic properties of 9 result from the different possible conformations of the compound which render the investigation of the flexibility of BACD dimers of major importance for targeted properties. As preliminary exploration of the potential of such O-annulated diimide structures in organic electronics, dimer 9 was investigated as a NFA for organic solar cells. After an optimization process detailed in Table , the highest power conversion efficiency (PCE) was recorded for cells where dye 9 was combined with the donor polymer PTB7-Th (PCE10) in 1:1 ratio, in an inverse architecture prepared as followed: