Earlier quoted context omitted.
Not unimaginable, a similar coating is on the inside of fluorescent lighting tubes.
Not really, the coating on fluorescent tubes uses a quite different mechanism. The phosphor coating of fluorescent tubes downconverts UV light into visible wavelengths (is, lower energy/frequency) through the process of fluorescence. The UV photons excite the electrons of the phosphor molecules to higher energy states, after which they emit photons at lower frequencies/energies (visible light) as they fluoresce back…
The purpose here is to make the light visible, not to do a 100% efficient conversion.