Computations are performed on Cz-BDT, Cz-AQ, Cz-BDT-SO 2 and Cz-BDF as shown in Fig. . The tertiary butyl groups used to improve solubility in the experimental studies have been excluded. Computations in this study are divided into three parts: (i) an initial optimisation of the ground state geometry, (ii) vertical excitations with different functionals, and (iii) excitedstate geometry optimisations in solution.