Thiol-end-functionalized Regioregular Poly(3-hexylthiophene) for PbS Quantum Dot Dispersions

Abstract

Inorganic nanoparticles hybridized with π-conjugated polymers were successfully synthesized by the ligand exchange reaction of thiol-end-functionalized regioregular poly(3-hexylthiophene) (P3HT-SH) with lead sulfide (PbS) quantum dots (QDs). The hybrid material (P3HT-SH/PbS-QD) shows good dispersibility in organic solvents even after 6 months due to the decreased intermolecular interaction of PbS nanoparticles coated by highly soluble P3HT. The ultraviolet–visible–near infrared absorption spectra show a clear difference in PbS-QDs hybridized with oleic acid and P3HT-SH, depending on the size of the PbS-QDs. By using transmission electron microscopy, small clusters of PbS-QDs are observed at the nanolevel when hybridized with P3HT-SH, indicating the formation of nanoscale aggregates of PbS-QDs in the hybrid material. Preliminary results for fullerene-free photovoltaic applications showed that P3HT-SH/PbS-QD can deliver almost two times higher power conversion efficiency (PCE) than P3HT when paired with an n-type naphthalene-diimide-based semiconducting polymer (N2200) as the photoactive system. Such an increase in PCE can be attributed to the increased dielectric constant exerted by PbS-QDs, which facilitates charge dissociation. This study not only describes a method for synthesizing PbS-QD-based organic–inorganic hybrids but also reveals an interesting design direction for photovoltaic materials.