Impact of neodymium doping on nitrogen enriched Co/CoS for high-performance dye-sensitized solar cells and supercapacitors

Abstract

Cobalt sulfide holds great promise for use in dye-sensitized solar cells (DSSCs) and supercapacitors due to its versatile properties. However, its practical application is often constrained by drawbacks such as low electrical conductivity, suboptimal nanostructuring, and limited long-term stability. This work addresses these limitations by introducing neodymium (Nd) doping into nitrogen-enriched cobalt/cobalt sulfide (Nd–N–Co/CoS). This enhances the structural and electronic properties by inducing lattice distortion and generating beneficial defects. Herein, Nd–N–Co/CoS samples are synthesized with varying neodymium doping levels (2%, 4%, and 6%) and used as counter electrodes in DSSCs. Among these, the 4% Nd-doped sample demonstrated superior electrocatalytic performance, showing the lowest charge transfer resistance in symmetric cells and achieving a power conversion efficiency (PCE) of 6.9%, which exceeds the efficiency (6.5%) of conventional platinum (Pt) electrodes under standard air-mass 1.0 global (AM 1.0G) illumination. Furthermore, symmetric supercapacitors were fabricated with the 4% Nd–N–Co/CoS electrode, which delivered a specific capacitance of 66.35 F g⁻¹, an energy density of 23.60 Wh kg⁻¹, and a power density of 1600 W kg⁻¹ at a specific current of 1 A g⁻¹. It also maintained a cycling stability of 94.51% and a Coulombic efficiency of 97.03% after 2000 cycles at 5 A g⁻¹, outperforming the undoped electrode. These findings highlight a promising approach for developing efficient electrode materials for next-generation energy conversion and storage technologies.