I'm not really sure what "sustaining the band gap" means. From my view it's not so much the "being liquid" part that's the problem. We often see this same problem in solids as well. When two (organic) fluorophores are brought in close contact, they interact, and typically in a fashion that quenches the luminescence. These interactions also usually attenuating the band gap, so maybe that's what he meant in the other thread. This doesn't always happen, but very frequently. In solution, you effectively isolate the fluorescing molecules.
There are species that have strong luminescence in the solid state. But you are limited with liquids because most fluorophores are complex organic molecules, and there are few complex organic molecules that are in the liquid state at room temperature.
For electroluminescence you have other concerns as well. I do not know of any examples that satisfy Nick Fury's needs, but that doesn't mean there aren't any. The immediate thing that comes to mind would be an organic fluorophore dispersed in an electrically conductive solvent medium. Investigating electrochemiluminescence (ECL) may be a good place to start looking.
https://en.wikipedia.org/wiki/Electrochemiluminescence