Structure and optical properties of carbon-TiO₂ composite thin films by sol-gel method as solar selective absorbers

C-TiO₂ thin films as low cost solar selective absorbers were prepared by sol-gel method and post-annealing. Differential scanning calorimetry (DSC), Raman spectroscopy, X-ray diffraction (XRD), High-resolution transmission electron microscope (HR-TEM), Field emission scanning electron microscopy (FE-SEM), UV-Vis-NIR spectrophotometer are employed to characterize the structure and optical properties. The results illustrated that C-TiO₂ composite thin films can be obtained after spinning and post-annealing. The solar absorptance (α) and thermal emissivity (ε) vary with carbon content and annealing conditions. The optimal annealing condition is 500 °C/2 h and the optimal carbon content is about 0.6 with α = 0.87 and ε = 0.13. C-TiO₂ composite thin films own good thermal stability at 100 °C, which proves that it can be a good candidate as low-temperature solar selective absorbers.