Transferred Chiroptical Transitions in Chiral Binaphthyl /π-Conjugated Polymer Hybrid Films: Significance of Aromatic Solvent-Mediated Co-Crystallization

Abstract

For advancing next-generation optoelectronics, a versatile strategy for fabricating pi-conjugated polymer (pi-CP)/chiral-small molecule (SM) hybrid films through co-crystallization-mediated chirality transfer is reported. The transfer of optical chirality from 1,1 '-binaphthyl-2,2 '-diamine (BN), a representative chiral inducer SM, to thin films of various achiral pi-CPs, including non-fluorene pi-CPs, is achieved by simply blending the pi-CPs with BN using aromatic organic solvents. The resulting pi-CP/chiral-SM hybrid films exhibit chiroptical responses at the main electronic absorption bands of various pi-CPs. Studies of the morphology, crystalline structure, and phase-separation structure of a representative hybrid system of poly(3-hexylthiophene) (P3HT) and BN reveal that these hybrid films exhibit a characteristic lamellar structure where the pi-CPs co-crystallize with chiral BN molecules, facilitated by aromatic solvent-assisted intermolecular pi-pi interactions. In-depth photophysical analysis suggests that BN molecules co-crystallized in the P3HT lamellar structure induce asymmetrically misaligned transition dipoles along the P3HT conjugated backbone, transferring optical chirality from BN to P3HT under circularly polarized light illumination. As a proof-of-concept, chiroptical photodiodes based on pi-CP/chiral-SM hybrid films and printed micropatterns, exhibiting a distinguishable photocurrent response depending on the direction of circularly polarized light are successfully demonstrated. A versatile strategy for fabricating pi-conjugated polymer (pi-CP)/chiral-binaphthyl (BN) molecule hybrid films is demonstrated. The use of aromatic solvent is critical for formation of co-crystalline structure, which induces chiroptical responses at the electronic transitions of various conjugated polymers in the hybrid films. The photodiode based on the hybrid film exhibit a distinguishable photocurrent response depending on the direction of circularly polarized light. image