Is IR radiative cooling of solar cells a valid efficiency improvement? I am interested in photonics and I stumbled across the following article:

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*E. Rephaeli, A. Raman, and S. Fan, "Ultrabroadband Photonic Structures To Achieve High-Performance Daytime Radiative Cooling", Nano Lett. 2013, 13, 4, 1457–1461.

But is IR radiative cooling really viable? If there's some water in the air,  it closes the "atmospheric window" that makes the outer space a cold heat sink. Also I see that this way of cooling is mainly researched by a small group of related researchers who reciprocally cite their articles.
So is it a really interesting option or just a kind of scientific hobby?
 A: I think such a technology has real application in space solar cells where heat management is real issue because it can only be managed via radiation. 
Maybe other applications include terrestrial concentrator photovoltaics. In these solar cells optics are used to concentrate sunlight up to around 1000x, so heat management again becomes important. However, probably easier to do with a heat sink. 
That said, conduction of heat is proportional to $\Delta T$ where as radiative cooling (in the blackbody limit - and these are not black emitters) is $\Delta T^4$. Also the heat sink temperature is on the order of 300K where as space is 2.7K! So intrinsically the temperature gradient is larger.
I can see potential for cost reductions too. That is, replacing any heat sink technology with a 2 micrometre layer incorporated into the growth process of the solar cell is attractive!
As for the point about it being niche and the circular references. Sometimes this is how things start. Someone has an idea, there is a flurry of activity and it dies away or it is picked up and ran with by everyone. I wouldn’t judge the quality of the science in that metric. 
