The polymers optimized in their ground states are shown in Fig. . We have replaced the side chains and saturated the polymer ends by hydrogen atoms to reduce the computational cost, which has only small effects on the electronic structure and optical excitations. We checked that all optimized polymers exhibit positive frequencies only, verifying the ground state optimization. Single point TD-DFT calculations of 30 singlet excited states are performed to calculate the excitation spectra for the optimized polymers. An ensemble of 1000 structures based on the nuclear ensemble approach is used to calculate an ensemble absorption spectrum. For both the single point TD-DFT as well as the ensemble approach the transitions are convoluted by Lorentzian shapes with a phenomenological broadening of 0.2 eV.