Bi^2+-doped strontium borates for white-light-emitting diodes

We report on Bi(2+)-doped SrB(4)O(7) and SrB(6)O(10) as orange and red phosphors for white-light-emitting diodes. In both compounds, absorption due to (2)P(1/2)-->(2)S(1/2) in Bi(2+) could be observed and quantified. The emission redshift from SrB(4)O(7) to SrB(6)O(10) and their different phonon satellite spectra are attributed to the enhancement of phonon-electron interaction. Investigation of the reduction mechanism of Bi(3+) to Bi(2+) suggests that in oxidizing atmosphere, Bi(2+) can be stabilized on Sr(2+) sites only in such lattices that are dominated by tetrahedrally coordinated boron.