A Review on Chalcogenide-Based Materials for Counter Electrode Applications in Dye-Sensitized Solar Cells: Sulfides, Selenides, and Tellurides

Dye-sensitized solar cells (DSSCs) have drawn attention in recent years for their cost-efficient, green, and convenient means of harnessing solar power. The function of DSSCs is designed around the counter electrode (CE), which is traditionally composed of platinum (Pt) for its good catalytic activity and good electric conductivity. However, Pt is expensive and in short quantity, and extensive studies have gone in search of substitute materials. Among them, materials in the system of chalcogenides, such as sulfides, selenides, and tellurides, have drawn considerable attention as potential candidates. These materials have various unique advantages, such as their capability to modulate their electronic property, good catalytic activity, and good resistance to chemicals, and therefore have good potential for optimizing function of DSSCs. This review presents an in-depth overview of where the situation stands in chalcogenide-based CEs, critically evaluating their synthetic routes, electrocatalytic activity, and stability. We compare and contrast various synthetic routes, such as hydrothermal, solvothermal, electrodeposition, chemical vapor deposition, atomic layer deposition, and solution-based synthesis, employed to alter the nanostructure and topography of such materials. Sulfide- and selenide-based materials have displayed competing power conversion efficiencies and favorable charge transfer behavior, but tellurides have potential through their exceptionally good electric conductivity. Despite such breakthroughs, limitations such as corrosion by the electrolyte, phase instability, and scalability of the routes of fabrication persist and serious bottlenecks persist. This review suggests possible strategies such as doping, composite formation, and formation of the protective layer to overcome such limitations and to ensure cost-efficient, high-performance DSSCs.