Performances of the PTR in the summer of 2022. (A) Simulated temperature profiles over time of the PTR at night. The device fast reaches a steady temperature and completes the phase change in 7.5 hours. Inset: the temperature field of the PTR at the eighth hour. The stored cold energy from radiative cooling can serve as an efficient heat sink during the daytime. (B) A schematic shows the test setups. The PTR is flipped with the CAB-hBN hybrid film facing the sky. A conventional radiative cooler is adopted for comparison. (C) Temperature comparisons between the PTR and a conventional radiative cooler. (D) Comparisons in cooling temperature (the difference between ambient temperature and temperatures of samples). Compared with a conventional radiative cooler, the PTR realizes a much larger cooling temperature, suggesting a better capacity in controlling the daytime temperature within the desired range. (E) Environmental conditions of the tests in (C and D). (F and G) Comparisons in cooling power and the corresponding environmental conditions, respectively. The temperature of the heating source is set as 22°C for both samples to compare the cooling power. (H) For areas with a large temperature difference between day and night, the PTR realizes much better (stabler) temperature regulation than the conventional radiative cooler. Color box: target temperature range (18 ± 3°C). The insert photograph shows the cloudy weather during the daytime tests. The PTR also weakens the dependence on the weather, a bottleneck of conventional radiative cooling that requires a clear day for excellent cooling performance.