Infrared absorption reflection and defraction

[princ3]

Please tell me about common materials which absorb IR sunlight radiation in the band of spectrum 1.1-2,5 microns and which will not allow the penetration of IR if some surface is covered with thin layer of them ?

 

[mfb]

What is "thin"?
If reflection is fine, just use metals.
Simple paint could work as well.

 

[princ3]

1/10 mm