Energy transfer and luminescence properties of Sr[1−3(x+y)/2]Al2B2O7:xEu3+, yBi3+ phosphor

Sr [1−3( x + y )/2] Al 2 B 2 O 7 : x Eu 3+ , y Bi 3+ ( x   =   0–5   mol% and y   =   0–5   mol%) phosphors are synthesized by a solid-state reaction method in air, and their crystal structure, fluorescence lifetime, and luminescence properties are investigated. The optimal composition is determined to be (Sr 0.94 Eu 0.03 Bi 0.01 )Al 2 B 2 O 7 . The PLE band peaks within the range 200–550   nm are due to O 2−   →   Eu 3+ charge transfer band, 7 F 0   →   5 H 3 , 5 D 4 , 5 L 7 , 5 L 6 , 5 D 3 , 5 D 2 , and 5 D 1 transitions, respectively. The strongest PL band peak under excitation 394   nm light is at ∼615   nm owing to 5 D 0   →   7 F 2 transition of Eu 3+ ion. The PL intensity of Eu 3+ , Bi 3+ co-doped SrAl 2 B 2 O 7 phosphor is 1.3   times that of Eu 3+ doped SrAl 2 B 2 O 7 phosphor due to the energy transfer between Eu 3+ and Bi 3+ ions, which is explained by the energy level diagrams of Bi 3+ and Eu 3+ ions. The CIE chromaticity coordinates of Sr 0.955 Al 2 B 2 O 7 :0.03Eu 3+ and Sr 0.94 Al 2 B 2 O 7 :0.03Eu 3+ , 0.01Bi 3+ phosphors under excitation 394   nm light are ( x   =   0.6292, y   =   0.3702) and ( x   =   0.6284, y   =   0.3711), respectively. These phosphors will be used as reddish orange emitting phosphor candidate for white LED with ∼394   nm near ultraviolet LED chip.