Fig. 4
Outdoor temperature performances of two photonic structures with same colour. a Photo of the temperature measurement apparatus on the test rooftop in Stanford, California. b Rooftop temperature measurements of the ‘cold’ (blue), ‘hot’ sample (red), a pink paint with similar colour (light purple) as well as a black paint (black), ambient air temperature (light grey), and solar irradiance (green) on a clear fall day in Stanford, California. In this measurement, a low-density polyethene film covers the apparatus to reduce the air convection effect, as shown in top schematic. c Rooftop temperature measurements of the same samples as Fig. 4b but allowing free airflow convection, to mimic the typical outdoor condition, as shown in top schematic
