Design and fabrication of NiSe₂/g-C₃N₄ hybrid composite counter electrode for Pt-free dye-sensitized solar cells

The aim of this study is to illustrate the feasibility of Pt-free Dye-Sensitized Solar Cells (DSSCs) at a reduced cost. To achieve this, we employed a straightforward ultrasonic-assisted hydrothermal method to synthesize composites consisting of NiSe₂ and different concentrations of 10%, 15%, and 20% of graphitic carbon nitride (NiSe₂/g-C₃N₄). These composites serve as electrocatalysts in the process of reducing tri-iodide to iodide within the DSSCs. The XRD, TEM, UV, Raman, and XPS spectra were employed to analyze the crystalline structure, morphology, and quantum states of these materials. NS-GN20 exhibited a high level of optical transmittance in the visible region, while a decrease in the optical bandgap was observed as the concentration of GN increased, decreasing from 1.82 to 1.56 eV. Cyclic voltammetry (CV) analysis of NS-GN20 electrodes revealed a more rapid reduction of triiodide ions at the electrode/electrolyte interface compared to the other electrodes. The 20% graphitic carbon nitride decorated NiSe₂ composite counter electrode outperformed the others with a remarkable power conversion efficiency (PCE) of 8.54%, accompanied by a short-circuit current (JSC) of 16.1 mA cm⁻² and an open-circuit voltage (VOC) of 0.686 V. The overall enhancement in photovoltaic performance can be attributed to the synergistic effects of highly catalytic NiSe₂ nanoparticles and the electrically conductive graphitic carbon nitride. Therefore, NiSe₂/g-C₃N₄ hybrid composite is expected to be an efficient and cost-effective CE material for DSSCs.