polymer chain.The influence of the o-dichlorobenzyl group on the miscibility between the polymer and PC71BM was studied by photoluminescence (PL) measurements. Fig. S1a and b show the PL spectra of the PC71BM films including various amounts of PTB7 or PTB7-DCB, which were recorded with excitations at 380 nm [7],and Fig. S1c exhibits a comparison of the normalized PL intensity