Engineering ZnO Nanopillars for Light Conversion Application through Tailored Substrate Properties

In this study, we present an investigation into the synthesis of ZnO nanopillars via electrodeposition techniques with a particular emphasis on the precise control of their nanometric diameters and their crystallographic orientation. The electrodeposition process was carried out on various substrates, including glass coated with transparent conducting oxides and platinum-coated silicon wafers. We analyze the influence of substrate properties (surface roughness and electrical conductivity) on the growth behavior of ZnO nanopillars, focusing on their crystallographic orientation, morphology, and coverage ratio. The role of surfactants in directing the electrodeposition process is also explored in depth. Among the surfactants tested, hexamethylenetetramine (HMTA) emerged as the most effective for promoting vertically aligned nanopillar growth. Furthermore, the influence of two different zinc precursors (acetate and zinc nitrate) has been studied. Our findings demonstrate that zinc nitrate improves the crystallographic texture and enhances photocurrent generation. The photoelectrochemical performance of the synthesized ZnO nanopillars is evaluated through measurements of the charge carrier transfer and recombination rates as a function of the applied potential. Remarkably, the nanopillars exhibit a charge transfer efficiency exceeding 80%, highlighting their strong potential for integration into photoactive devices, such as solar cells. This study underscores the critical role of substrate selection, surfactant chemistry, and precursor choice in tailoring ZnO nanopillar growth and optimizing their optoelectronic properties for energy conversion applications.