Influence of Alcohol-Based Brighteners on the Morphology and Structure of Electroplated Nickel: Experiments and Theoretical Calculations

To increase the electrical conductivity of nickel electrodes used in solar cells, this study investigated the effects of six different alcohol-based brighteners on nickel electrodeposition and elucidated their mechanisms during the deposition process. Nickel electrodeposition was conducted on a single-crystal silicon (c-Si) substrate in a Watts nickel plating bath with the addition of various additives at 1 g/L. Surface analysis and microstructure characterization were employed, alongside density functional theory calculations and molecular dynamics simulations, to analyze the influence of brightener molecule adsorption on metal grain growth and conductivity properties. These results indicate that alcohol-based additives can be automatically absorbed on the surface of the deposit, whereas long-chain polyhydroxy additives result in a smaller energy gap ( \(\Delta E\) $\mathrm{\Delta }E$ ) and more active adsorption sites than do short-chain additives, facilitating greater reactivity on the Ni surface. This resulted in a preferred orientation shift of the crystal structure from the (200) plane to the (111) plane, along with a refined grain size and conical morphology growth. Among the studied additives, long-chain molecules increased the Ni⁰ content in the plating layer and increased its conductivity. In particular, sorbitol effectively reduced the resistivity and grain growth rate of the coating, underscoring its potential as an additive for fabricating high-performance electrodes on c-Si substrates.