Interfacial treatment insights of promising ternary Cu-doped ZnO–GO thin films for improved silicon surface passivation

Copper (Cu)-incorporated (0 to 2 at.%) Zinc oxide (ZnO)-Graphene oxide (GO) nanostructures were synthesized via a hydrothermal technique and spin-coated on silicon (Si) substrates. Structural analysis using X-ray diffraction (XRD) and atomic force microscopy (AFM) confirmed the successful formation of well-crystallized ZnO nanoparticles on GO sheets, with AFM revealing a decrease in grain size as the Cu incorporation concentration increased, resulting in smoother and more homogeneous surfaces. Optical studies revealed a reduction in the bandgap to 3.241 eV for 2 at.% Cu-treated films, compared to pure ZnO. Alongside this, photoluminescence (PL) emission intensity decreased as the Cu concentration increased. Furthermore, optical reflectance measurements showed a gradual decrease in reflectance with increasing Cu incorporation, indicating improved light absorption. The carrier lifetime of the Si and Cu-incorporated ZnO–GO/Si samples significantly increased, with the 2% Cu-doped sample reaching 165 μs. These results highlight that Cu incorporation in ZnO–GO improves surface passivation by reducing recombination sites and enhancing light absorption, making it a promising material for silicon-based devices, particularly in photovoltaic applications.