To classify the monomer into strong and weak acceptors and donors, we needed to set a relative scale because absolute HOMO eigenvalues highly depend on the DFT functional and basis set used. Some have used thiophene as a "spacer" monomer in various π-conjugated polymers, as it is claimed to not affect the electronic properties significantly . For the same reason, some have used thiophene as a reference monomer when comparing different donor and acceptor monomers. Therefore, we looked at the relative HOMO and LUMO eigenvalues, as well as the HOMO-LUMO gap and the stability of their triplet state (∆E T -S ) for all monomers (Figure ). The single-point calculations using the ωB97X-D3 functional followed the same steps as the full oligomers, as described in Section 2.3.2.