Step-by-step build-up of ordered p–n heterojunctions at nanoscale for efficient light harvesting

Abstract

A simple “grafting from” strategy is reported to graft polymer brushes bearing thiophene groups onto TiO₂ nanowires via a surface initiated polymerization and FeCl₃ catalytic oxidized polymerization. Subsequently, the in situ CdS nanocrystals can be fabricated along the conductive polymer network, enabling highly ordered p–n heterojunctions to be prepared on the nanoscale. Polynorbornene bearing thiophene was grafted onto TiO₂ nanowires via surface-initiated ring-opening metathesis polymerization (SI-ROMP), and then the oxidization polymerization of the thiophene derivative was performed to prepare conductive conjugated polythiophene brushes. The carboxyl groups in conductive polymer brushes can be used as the source precursor to coordinate cadmium cations for templating CdS nanocrystal formation, meanwhile creating intimate interfacial contact between nanocrystals and conjugated polymers. This novel approach offered a superior platform to the step-by-step build-up of ordered heterojunctions on the nanometer scale and has great advantages in precisely controlling the detailed nano-morphology and dispersion of nanocrystals within conductive polymers.