One-step in situ hydrothermal fabrication of D/A poly(3-hexylthiophene)/TiO2 hybrid nanowires and its application in photovoltaic devices

Abstract

In this study, we developed a novel in situ hydrothermal method to fabricate self-assembled P3HT/TiO₂ hybrid nanowires, wherein a facile one-step synthetic strategy was utilized to co-organize P3HT molecules and titanium precursors into highly elongated hybrid nanowires, followed by a hydrothermal process in an autoclave to in situ transform the titanium precursors into crystalline TiO₂ nanoparticles on the P3HT nanofibrils. P3HT nanofibrils were utilized as a structure-directing motif to achieve a favorable dispersion of electron acceptor (A) TiO₂ nanocrystals of 10–15 nm in diameter embossed along the nanofibrils, as well as an efficient electron donor (D) for the nanohybrid. In particular, the crystallization temperature of anatase-phase TiO₂ nanoparticles with high crystallinity obtained via the hydrothermal method was significantly reduced to 130 °C in an elevated pressure of ∼7 bars as compared to the conventional calcination temperature of 450 °C at ambient pressure for TiO₂ nanocrystal synthesis, therefore, allowing the synergistic one-step fabrication of both highly crystalline TiO₂ nanoparticles embossed on highly crystalline long-range ordered P3HT nanofibrils. As a consequence of the structural development, this P3HT/TiO₂ embossed nanohybrid could afford significant improvements in its D/A interfacial contact area for effective charge separation without the need for capping ligands typically used in ex situ D/A blend systems, as well as an efficient pathway for charge transport, leading to enhanced optoelectronic properties and device performance. The highest conversion efficiency of 0.14% was presented by the P3HT/TiO₂ embossed hybrid device, which was a remarkable improvement as compared to only 0.03% from an ex situ P3HT/TiO₂ hybrid device. This novel in situ approach shows a feasible way to fabricate organic/inorganic nanohybrid materials of conjugated copolymers with different inorganic nanoparticles for the applications of future optoelectronic devices.