Cost-effective and morphology-controllable niobium diselenides for highly efficient counter electrodes of dye-sensitized solar cells

Abstract

Developing Pt-free and highly efficient counter electrodes (CEs) is meaningful and necessary for the cost reduction of dye-sensitized solar cells (DSCs). In this work, via a facile and reductant-free solvothermal approach, we report the controllable synthesis of NbSe₂ nanosheets (NSs), nanorods (NRs), as well as the composite NbSe₂/C for use as CEs in high efficiency DSCs. The morphology and structure of the three samples were characterized by SEM, XRD and TEM. Meanwhile, by cyclic voltammetry measurements, electrochemical impedance spectroscopy and Tafel polarization, we found some key issues which explain the difference in their electrocatalytic activity in the reduction of triiodide (I₃⁻). Compared with electrodes based on NbSe₂ NRs, NbSe₂ NS-based CEs demonstrated lower resistances in charge transfer and ionic diffusion. Subsequently, DSCs with NbSe₂ NS-based CEs achieved a conversion efficiency of 7.34%. In addition, NbSe₂/C composite-based CEs could further reduce the series resistance and finally a conversion efficiency of 7.80% was obtained, comparable to an efficiency of 7.90% for Pt-based CEs. The NbSe₂ in our work provides a cost-effective CE alternative to the noble metal Pt in DSCs.