And that surrounding air will radiate thermal infrared back heating the panel. As was pointed out in another thread, this still may work, but not as efficient as long as some infrared is not absorbed.
No significant difference. The point is that the more opaque the air is to infrared, the more your panels are in thermal equilibrium with the surrounding air (ambient air temperature) rather than space (2.7K). They're in equilibrium with a weighted combination of those. Doesn't matter whether you heat up the surrounding air by 0.01 degrees.