Singlet Exciton Delocalization in Gold Nanoparticle-Tethered Poly(3-hexylthiophene) Nanofibers with Enhanced Intrachain Ordering

We fabricated hybrid poly­(3-hexylthiophene) nanofibers (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 (S₁) 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

Elucidating the Chain-Extension Effect on the Exciton-Dissociation Mechanism through an Intra- or Interchain Polaron-Pair State in Push–Pull Conjugated Polymers

We elucidated chain-extension effects of a benzodithiophene (BDT) and thienopyrroledione-based push–pull conjugated polymer (CP) on its exciton-dissociation mechanism within aggregate systems using transient absoption spectroscopy. The side-group extension CP with benzothiophene on the BDT unit induced H-type excitons with excess energy owing to decreased chain stiffness. This led to interchain polaron-pair (PP)-mediated exciton dissociation. The stiff side-group extended with thienothiophene on the BDT unit also induced H-type excitons, but the decreased energy and breadth of the density of states suppressed the interchain PP-mediated exciton dissociation. The main-chain-extension CP with two thiophenes on either side of the BDT unit has a curved structure disturbing the interchain packing. Thus, the driving force of exciton dissociation between the chains decreased, leading to intrachain PP-mediated exciton dissociation. Our findings can facilitate the development of novel CPs to further increase the efficiencies of polymer solar cells