Synthesis of Highly Effective Vanadium Nitride (VN) Peas as a Counter Electrode Catalyst in Dye-Sensitized Solar Cells

Vanadium nitride (VN) peas and cubes were synthesized by regulating the molar ratio of the starting materials (urea/VOCl3) via the urea-metal chloride route. The as-prepared VN compounds were subsequently introduced into dye-sensitized solar cells (DSCs) as counter electrode (CE) catalysts for the regeneration of novel organic thiolate/disulfide (T-/T-2) and traditional iodide/triiodide (I-/I-3(-))redox couples. The cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel polarization curve results proved that the catalytic activity of the prepared VN was significantly affected by particle shape and particle size. The VN peas showed the highest catalytic activity, followed by the small VN cubes and large VN cubes. The I-/I-3(-)-electrolyte-based DSCs yielded a high power conversion efficiency (PCE) of 7.29%. The Pt-free VN CE catalysts are more suitable for the new organic redox couples of T-/T-2. The DSCs based on VN peas CE showed a PCE of 5.57%, an enhancement of 40.7% relative to the Pt-CE-based DSCs (3.96%).