Normally, in LEDs and solid state lasers, there is a direct relation between wavelength(energy quantum) (electron-Volts) and operating voltage (Volts).
For example Red = 660 nanometers = 1.8 electron-Volts = 1.8 Volts, which is the typical operating voltage for a Red LED.
Blue = 470 nm = 3.3 eV = 3.3 Volts operating voltage.
So: Deep UV (270 nm) is supposed to operate on ~4.6 Volts.
But article mentions 13.8 Volts. I wonder why there is such a huge gap?