Figure 2 (a) Optimized geometries (top: top view; bottom: side view) of the three NFREAs. (b) 2D-GIWAXS patterns of neat NoCA-17, NoCA-18, and NoCA-19 films.
compared to IC-2Cl, leading to a more efficient intramolecular charge transfer effect. Accordingly, NoCA-19 displays a blue-shifted absorption peak (728 nm) in comparison NoCA-18. Both symmetric acceptors, NoCA-17 and NoCA-18, in the thin film exhibit comparable absorption spectra. In contrast, the asymmetric acceptor NoCA-19 demonstrates a broadening of the absorption spectrum in the high-energy region, indicating a unique stacking arrangement in the solid state.
Table 1 Basic properties of NoCA-17, NoCA-18, and NoCA-19