Having provided a detailed analysis of Cz-BDT and Cz-AQ, we will now proceed to two additional molecules, alluded to briefly in the introduction and shown in Fig. (i) Cz-BDT-SO 2 containing an oxidised derivative of the BDT acceptor, with two oxygen atoms bound to each sulfur atom; and (ii) Cz-BDF, the benzodifuran derivative of BDT, where the sulfur atoms are replaced with oxygen atoms. As opposed to Cz-BDT and Cz-AQ, which have been synthesised and well-characterised, these two molecules have not yet been synthesised.