The sun and outer space are the ultimate heat and cold sources for the earth,respectively.They have significant potential for renewable energy harvesting.In this paper,a spectrally selective surface structure that has a planar polydimethylsiloxane layer covering a solar absor-ber is conceptually proposed and optically designed for the combination of photothermic conversion(PT)and night-time radiative sky cooling(RC).An optical simulation is conducted whose result shows that the designed surface structure(i.e.,PT-RC surface structure)has a strong solar absorption coefficient of 0.92 and simultaneously emits as a mid-infrared spectral-selective emitter with an average emissivity of 0.84 within the atmospheric window.A thermal analysis prediction reveals that the designed PT-RC surface structure can be heated to 79.1℃ higher than the ambient temperature in the daytime and passively cooled below the ambient temperature of approximately 10℃ in the nighttime,indicating that the designed PT-RC surface structure has the potential for integrated PT conversion and nighttime RC utilization.