Tunable white light emitting Sr 2 V 2 O 7 :Bi 3+ phosphors: Role of bismuth ion

Phase purity, optical properties and defects in new near white light emitting rare earth free Sr2V2O7:Bi3+phosphors were investigated. Emission spectrum of Sr2V2O7 displayed two peaks at all excitation wavelength approximately around 450 (P1) and 600nm (P2). With increase in the excitation wavelength; emission intensity increases and there is a red and blue shift in Peak P1 and P2, respectively. On bismuth doping, the two Peaks P1 and P2 slowly starts merging and become a single broad peak at 5% doping. Bismuth doping also reduces the emission peak energy. This is attributed to substitution of Bi3+ at Sr2+ site which would distort VO4 tetrahedra, thereby reducing the energy difference between the 3T and 1A levels of VO43− distorted tetrahedral. This dual role of bismuth doping and excitation energy leads to interesting tunability in white emission from cool to warm white. This opens a new arena in phosphor research because of great role of white LEDs (both warm and cool) in outdoor and indoor lighting. Keywords: White light, Pyrovanadate, Photoluminescence, Positron annihilation, Phosphors, Tunable