A structural polymer for highly efficient all-day passive radiative cooling

All-day passive radiative cooling has recently attracted tremendous interest by reflecting sunlight and radiating heat to the ultracold outer space. While some progress has been made, it still remains big challenge in fabricating highly efficient and low-cost radiative coolers for all-day and all-climates. Herein, we report a hierarchically structured polymethyl methacrylate (PMMA) film with a micropore array combined with random nanopores for highly efficient day- and nighttime passive radiative cooling. This hierarchically porous array PMMA film exhibits sufficiently high solar reflectance (0.95) and superior longwave infrared thermal emittance (0.98) and realizes subambient cooling of similar to 8.2 degrees C during the night and similar to 6.0 degrees C to similar to 8.9 degrees C during midday with an average cooling power of similar to 85W/m(2) under solar intensity of similar to 900W/m(2), and promisingly similar to 5.5 degrees C even under solar intensity of similar to 930W/m(2) and relative humidity of similar to 64% in hot and moist climate. The micropores and nanopores in the polymer film play crucial roles in enhancing the solar reflectance and thermal emittance. There still remains a big challenge in fabricating highly efficient and low-cost radiative coolers for all-day and all-climates. Here, the authors report a hierarchically structured polymethyl methacrylate film with a micropore array combined with random nanopores for highly efficient day- and nighttime passive radiative cooling.

Automated summary

The authors present a hierarchically structured polymethyl methacrylate film with a micropore array combined with random nanopores for highly efficient day- and nighttime passive radiative cooling, achieving high solar reflectance and longwave infrared thermal emittance. There is still a challenge in fabricating highly efficient and low-cost radiative coolers for all-day and all-climates.