Warm-white LED with ultra high luminous efficacy due to sensitisation of Eu3+photoluminescence by the uranyl moiety in K4(UO2)Eu2(Ge2O7)2

A warm-white LED with a CCT of 2700 K and a very high LE of 360 lm W_opt⁻¹was fabricated by use of K₄(UO₂)Eu₂(Ge₂O₇)₂as the red emitter. A highly efficient uranyl to Eu³⁺energy transfer is utilized for sensitisation. This is the first report of a Eu³⁺activated phosphor being successfully employed on a blue emitting (In,Ga)N LED.