We fabricated hybrid poly(3-hexylthiophene) nano fibers (P3HT NFs) with rigid backbone organization through the self-assembly of P3HT tethered to gold NPs (P3HT-Au NPs) in an azeotropic mixture of tetrahydrofuran and chloroform. We found that the rigidity of the P3HT chains derives from the tethering of the P3HT chains to the Au NPs and the control of the solubility of P3HT in the solvent. This unique nanostructure of hybrid P3HT NFs self-assembled in an azeotropic mixture exhibits significantly increased delocalization of singlet (S-1) excitons compared to those of pristine and hybrid P3HT NFs self assembled in a poor solvent for P3HT. This strategy for the self-assembly of P3HT-Au NPs that generate long-lived S1 excitons can also be applied to other crystalline conjugated polymers and NPs in various solvents and thus enables improvements in the efficiency of optoelectronic devices.