Electrodeposition of Cu thin film assisted by Cu nanoparticles for Cu₂ZnSnSe₄ solar cell applications

Electrodepositing high-quality Cu thin film on Mo substrate is important for fabricating high-efficiency Cu₂SnZnSe₄ (CZTSe) solar cells via the electrodeposition technique. In this study, a novel route to modify the surface morphology of Cu thin film is reported by utilizing pre-embedded Cu nanoparticles on Mo substrate. The Cu nanoparticles with controlled size and density are synthesized after soaking the pre-fabricated Cu thin films in HCl solution. After employing these Cu nanoparticles to act as nuclei points during the electrodeposition process, compact and flat Cu thin films are successfully electrodeposited in simple salt solution (with no additives) without the precise control of substrate properties and deposition parameters. Due to the electrodeposition of high-quality Cu thin films, CZTSe thin films with compact and uniform grains are prepared. As a result, the carrier density in the CZTSe absorber is significantly improved and a deep level defect induced by the poor morphology metal precursor is inhibited. Finally, a CZTSe solar cell with a power conversion efficiency of 7.36% is fabricated.