Flicker Reduction of AC LEDs by Mn2+ Doped Apatite Phosphor

This work presents some flicker reducing phosphors according to the composition Sr-5(PO4)(3)Cl:Eu2+Mn2+, which are excitable between 380 and 450 nm and exhibit an emission spectrum ranging from 550 to 620 nm. Flicker is defined as the rapid variation in light source intensity and it is still a drawback of modern AC driven LEDs, which are not electrically smoothened by a driver. Recently, a lot of effort is dedicated to the electrical smoothening of LED flicker. Instead of using a driver system, this work concentrates on a phosphor, which emits light during the dead time of the LED chip. Due to the slow decay of the forbidden transition of Mn2+ and an efficient excitation transfer from Eu2+ to Mn2+ a white light emitting LED system with a percent flicker of about 30% and a flicker index of 0.08 was achieved. A white color point was created by using an optimized doping concentration of Eu2+ and Mn2+ in the Sr-5(PO4)(3)Cl:Eu2+Mn2+ and a 400 nm LED as excitation source. (C) 2018 The Electrochemical Society.