▎ 摘　　要

Dye-sensitized solar cell (DSSC) technology could become a low-cost solution for solar energy harvesting if the use of expensive dyes and Pt can be avoided. This work reports the development of novel nanohybrid thin films based on CoNi2S4 nanotubes embedded on sheets of reduced graphene oxide (rGO), which can serve as an excellent counter electrode for DSSC showing great promise to replace Pt. The structural and morphological characterization of the nanocomposite films synthesized using a simple one-step hydrothermal method revealed well-defined crystalline nanotubes of CuNi2S4 (with length 200 nm and diameter 10.41 nm) uniformly embedded on the surfaces of the rGO sheets (similar to 2.65 mu m in size). The optimized CuNi2S4/rGO nanohybrid film when used as counter electrode in DSSC, photo conversion efficiency as high as 9.68 +/- 0.02% was recorded, a value almost equal to that obtained from the DSSC fabricated with Pt as counter electrode (7.01 +/- 0.01%) and much higher than that with bare CuNi2S4 (5.01 +/- 0.01%) justifying its potential use in Pt-free DSSC. The improved performance of the electrode have been attributed to the hierarchical nanohybrid structure consisting of 1D CuNi2S4 nanotubes embedded on electrically conducting 2D rGO sheets that provides fast ion diffusion pathways, large accessible surface area and good chemical and thermal stability.