Facile Synthesis of V<sub><i>x</i></sub>A<sub>1–<i>x</i></sub>(<i>x</i> = 0–1, A= C, O) Multiphase Composites Derived from Polyoxovanadate Precursors by Pyrolysis along a Temperature Gradient as Pt-free Counter Electrodes for High-Efficient Dye-Sensitized Solar Cells
Kezhong Wu, Yingshan Wu, Shan Liu, Bei Ruan, Jianing Guo, Mingxing Wu
Abstract
Replacing precious Pt-based counter electrodes (CEs) with a low-cost and high-performance Pt-free catalyst of CEs is still in urgent need to decrease the fabrication cost of dye-sensitized solar cells (DSSCs). Herein, the elements V and A (A = C, O) of the final state of the target materials are prefabricated in an organic complex precursor by bonding, and then, the precursor was directly processed to prepare VxA1–x(x = 0–1, A = C, O) multiphase CE catalysts by pyrolysis along the temperature gradient under N2 flow, which further served as catalytic materials of CEs for the encapsulation of DSSCs. The precursors were obtained utilizing polyoxovanadate (NH4)2V6O16 as a metal source and glucose as a carbon source via a facile hydrothermal method. Power conversion efficiencies of 5.38, 6.29, 6.60, 6.82, and 6.23% were obtained from the five different VxA1–x(x = 0–1, A = C, O) multiphase CE catalysts as CEs to reduce iodide/triiodide in DSSCs, which were prepared at pyrolysis temperatures of 600, 700, 800, 900, and 1000 °C, respectively. The enhanced performance of VxA1–x materials can be attributed to the more catalytic active site number and the high conductivity, which is due to the higher specific surface area provided by the pyrolysis and carbonization of glucose and the activation and modification of materials at high temperature and N-doping. The impressive finding in this work indicates that the VxA1–x composite can be considered as a promising candidate for low-cost and high-efficient CEs in the fabrication of DSSCs.