Alloy-based metallic nanoparticles for enhanced solar cell performance: materials and device insights

Alloy-based metallic nanoparticles (NPs) have attracted increasing attention as promising materials for improving solar cell (SC) performance because of their tunable optical, electrical, and catalytic properties, which can provide advantages over their monometallic counterparts. This review examines the application of alloy-based metallic NPs, including Au-Ag, Pt-Co, Ni-Cu, and Fe-Ni systems, in different SC technologies. Although alloy NPs have been explored in silicon, perovskite, organic, and dye-sensitized solar cells (DSSCs), this review places greater emphasis on DSSCs due to the larger number of reported studies in this area. The fundamental characteristics of alloy NPs are discussed, with particular attention to the effects of composition, synthesis strategies, and structural features on their optical, electronic, and catalytic performance. These properties enable alloy NPs to improve light harvesting, facilitate interfacial charge transfer, and enhance catalytic processes when incorporated into SC architectures. In DSSCs, both Pt-based and Pt-free alloy NPs, often combined with conductive carbon materials, have demonstrated reduced charge-transfer resistance and improved electrocatalytic activity, leading to enhanced fill factor and power conversion efficiency. However, the resulting improvements are strongly influenced by factors such as alloy composition, NP morphology, and integration strategy. The review also summarizes the roles of alloy NPs in other SC platforms, including plasmonic light trapping and antireflection effects in silicon cells, near-field enhancement and scattering effects in perovskite cells, and localized surface plasmon resonance-mediated absorption improvement in organic SCs. A comparative analysis is provided to highlight the performance benefits, limitations, and trade-offs associated with different alloy systems. Finally, key challenges, including scalable synthesis, environmental considerations, and insufficient long-term stability evaluations under practical operating conditions, are discussed. Future research directions are proposed, emphasizing the need to balance efficiency improvements with cost, scalability, and durability for the successful implementation of alloy NPs in next-generation solar technologies.