Infrared to green conversion of long persistent luminescent Eu 2+ -Dy 3+ Co-doped SrAl 2 O 4

The infrared to green conversion of long persistent luminescent SrAl 2 O 4 :(Eu 2+ , Dy 3+ ) phosphors has been investigated experimentally. It is found that the infrared light with the wavelength 1350 nm and 1550 nm can be converted to green light by the phosphors. Experimental evidences show that there exist two possible mechanisms which are responsible for the infrared to green conversion: one is the excitation of the electron in the trap energy levels of the phosphors to the higher energy levels of Eu 2+ ions by absorbing one infrared photon; the other is the excitation of the electron in the ground energy levels of Dy 3+ ions to the higher energy levels of Dy 3+ ions by absorbing two infrared photons. The easy fabrication and low cost make the phosphors a promising candidate of photovoltaic materials.