Exceptional photoconductivity of poly(3-hexylthiophene) fibers through in situ encapsulation of molybdenum disulfide quantum dots

Abstract

Photo-responsive, electrically conductive nanostructures are highly desirable for wide-ranging applications in energy harvesting, nanophotonic and optoelectronic devices. To this end, we realize self-assembled, photoconductive hybrids of poly(3-hexylthiophene) (P3HT) micro- and nano-fibers integrated with MoS₂ quantum dots (QDs). We present an innovative strategy to impregnate QDs within the walls of the P3HT fibers resulting in the emergence of the controllable photoconductivity of the QD-P3HT hybrid. The maximum photoconductivity (>80% higher than pristine P3HT) is observed at 360 nm and originates from a synergistic combination of (a) defect healing and quenching of surface trap states in QDs by P3HT and (b) efficient generation and transfer of photo-excited charges from P3HT to QDs. This mechanism is substantiated by a concomitant decrease in the excited-state lifetime of the QD-P3HT hybrid. Furthermore, a linear correlation between the enhancement in the emission of QDs and the emission quenching of P3HT supports the proposed mechanism of excited-state charge transfer. Finally, the hybrid of MoS₂ nanosheets (NS) with P3HT fibers (NS-P3HT) does not exhibit any photo-conductivity and instead exhibits ground state charge transfer, underlying the critical role of quantum confinement effects operating in the QD-P3HT hybrid. Thus, we demonstrate a synergistic, self-assembled QD-P3HT hybrid exhibiting optically controllable electrical conductivity in the solid state as novel functional materials for optoelectronic applications.