PDRCs can be broadband in their thermal emittance capacity, meaning they possess high emittance in both the solar spectrum and atmospheric LWIR window (8 to 14 μm), or selective emitters, meaning they narrowband emit longwave infrared radiation only in the infrared window.
In theory, selective thermal emitters can achieve higher cooling power. However, selective emitters also face additional challenges in real-world applications that can weaken their performance, such as from dropwise condensation, which is common even in semi-arid environments, that can accumulate on the PDRC surface even when it has been made hydrophobic and alter the narrowband emission. Broadband emitters also outperform selective materials when "the material is warmer than the ambient air, or when its sub-ambient surface temperature is within the range of several degrees."
Both emitters can be advantageous for different types of applications. Broadband emitters may be less problematic for horizontal applications, such as on roofs, whereas selective emitters may be more useful if implemented on vertical surfaces like building facades, where dropwise condensation is inconsequential and their stronger cooling power can be actualized.
Broadband emitters can be made angle-dependent to potentially enhance their cooling performance. Polydimethylsiloxane (PDMS) is a common broadband emitter used for PDRC. Most PDRC materials are broadband primarily credited to their lower cost and higher performance at above-ambient temperatures.