Dual electrical-behavior regulation of α-MoC quantum dots and Mo-N-C sites for high photoelectric conversion performance of solar cells

Constructing low-price yet high-efficiency counter electrode (CE) materials for dye-sensitized solar cells (DSSCs) is vital in the field of energy conversion. Herein, α-MoC quantum dots (QDs) decorated with Mo-N-C sites are encapsulated in a unique carbon flower structure (CF) as efficient CE (α-MoCQD@NCF). The α-MoCQD@NCF CE in DSSC exhibits high power conversion efficiency (PCE) with up to 9.12%, which greatly exceeds that of pure Pt (7.53%). Electron microscopy reveals that α-MoCQD@NCF is an ultrathin-hierarchical hollow structure, which promotes the sufficient contact of the electrolyte. Simultaneously, the ultra-small size of α-MoCQD is beneficial for maximizing the utilization of active sites to accelerate the triiodide reduction reaction. Additionally, theoretical calculations disclose that atomically engineered Mo-N-C sites combined with α-MoCQD can complement and reinforce each other to transfer electrons to the carbon matrix. Therefore, through the synergistic effect of the dual regulation of electron transfer rate and pathway, the electron transfer on the CE surface is accelerated, the iodide ion coupling is restrained and the reaction kinetics are improved. It not only offers a rational approach to develop low cost and high activity electrode material, but also opens an avenue for other energy-related fields.