“…That was possible due to the absence of efficiency droop in ZnO, whereas droop is typical for commercial nitride LEDs at high carrier densities. Thereafter, hydrothermal ZnO UV LEDs could be applied for safe UVA disinfection of touch screens [ 23 ], pumping of white phosphors for lighting [ 24 ], and ultra-bright micro-LEDs for displays [ 25 ].…”