Hydrothermal synthesis and piezoelectricity of p-SnO nanoparticle/n-ZnSnO₃ nanorod array heterojunction films

We investigated the hydrothermal fabrication of n-ZnSnO₃ nanorod array films decorated with various ratios of p-SnO nanoparticles on fluorine-doped tin oxide substrates and their synergistic piezoelectricity-induced applications. We used Mott–Schottky measurements and an energy band diagram to determine the materials’ conductivity type. The associated current–voltage characteristics and charge transport behavior were elucidated by investigating Schottky barriers, Schottky emissions, tunneling, depletion regions, and piezopotential-induced energy band bending. The piezoelectric coefficients (d₃₃) of the ZnSnO₃ nanorod array and the Composite II film were measured to be approximately 15.4 and 17.3 p.m.·V⁻¹, respectively. Theoretical simulation of piezopotential distributions revealed that compressive deformation was predominant for samples under stress. The Composite II film exhibited reliable piezophotodegradation activity for rhodamine B (RhB) solutions, with a degradation rate constant of approximately 1.2 × 10⁻² min⁻¹ under visible-light irradiation, approximately 2.5 times that of the individual ZnSnO₃ film, partially due to intimate contact between the two constitutive components, high electrochemical surface areas, and facilitated charge carrier transport resulting from piezopotential-induced energy band bending. This study revealed the positive effect of piezoelectricity on photodegradation and established a paradigm to allow wide-bandgap materials to function in the visible-light range through a p–n junction.