In theory, the way fluorescent light-bulbs work, is that they already have a light-source of shorter wavelength – and therefore of higher photon-energy – to excite a phosphor, the latter of which emits a pleasant mixture of wavelengths of light – in general, longer wavelengths than that of the energy-source; any mixture of phosphors will do. The light source is allowed to be a Blue LED, rather than a UV light-source.
What I discover in practice, is that the choice of phosphors manufacturers can work with is rather limited. For LED-Light-Bulbs that are stated to produce a color-temperature of 2700K, they tend to use “Y3Al5O12Ce”. Additionally, I have discovered the availability of a newer type of light-bulb, as shown in this photo:
In which a higher voltage is applied directly to an Electroluminescent material.
What strikes me as both convenient and remarkable about these light-bulb-types, is that The color matches very closely. What this observation would seem to suggest, is that the EL material used in the newer light-bulb-type is a hard crystal, that matches the composition of the phosphors used in the LEDs, mentioned above. Additionally, this would seem to suggest, that the layer of the phosphors used in the LED-Light-Bulbs described as having 2700K color, is rather thick, so that very little of the Blue LED’s light passes through, since the light produced via EL has no Blue LED to modify its color-quality.
I suppose then, that the manufacturers have simply added another substance to this phosphor – in small quantities – that causes it to become conductive.