Figure 1. Molecular structures of helical perylene diimide oligomers and polymers.

(a) Chemical structures of hPDI3, hPDI4, PTB7 and PTB7-Th. (b) Schematic of the energy levels of hPDI3, hPDI4, PTB7 and PTB7-Th. Energy levels of PTB7 and PTB7-Th were adopted from ref. 7 and ref. 5, respectively. Energy levels of hPDI3 and hPDI4 were adopted from ref. 21. (c) Molecular model of hPDI4 in a waggling conformation from DFT calculations. Hydrogens and alkyl side chains have been removed for clarity. Black, carbon; red, oxygen; blue, nitrogen. (d) Film absorption spectra of hPDI3, hPDI4, PTB7 and PTB7-Th normalized at their low-energy λ_max.