In this study, the spectrally selective solar absorber coatings of TiN/Al₂O₃ are deposited onto stainless steels (SS) at a high substrate temperature of 300 °C, which exhibits a high absorptance of 0.92 and a low emittance of 0.11 at 82 °C. The structure, optical properties and thermal stability have been characterized by ultra-high resolution scanning electron microscopy, UV–vis–NIR spectrophotometry, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The study's results indicate that the substrate temperature (300 °C) has an important effect on the solar absorptance and emittance. The SS/TiN/Al₂O₃ coating exhibits good thermal stability in a vacuum at 500 °C for 5 h. The coating also exhibits good thermal stability in air at 200 °C for 2 h. Raman analysis confirms that the oxidation of the SS/TiN/Al₂O₃ coating in air causes the composition to approach the stable oxide TiO₂.