Color-tunable emission and energy transfer in Tm3+/Dy3+/Sm3+ tri-doped phosphate glass for white light emitting diodes

Re3+ (Re3+=Tm3+, Dy3+, Sm3+) ions doped phosphate glasses for white light emitting diodes (W-LEDs) are successfully prepared by the high-temperature melting method. The luminescence properties of the glasses were characterized by the emission and excitation spectra. When excited by ultraviolet light Tm3+ ions single doped, Dy3+ ions single doped, and Sm3+ ions single doped phosphate glass emit blue, green and red light, which give the characteristic transitions of Tm3+ ions (1D2→3F4), Dy3+ ions (4F9/2→6H13/2,15/2), and Sm3+ ions (4G5/2→6H7/2,9/2), respectively. Moreover, there exists simultaneous luminescence of Tm3+, Dy3+, Sm3+ ions individually when co-doping them in the single phased phosphate glass (for example, Tm3+/Sm3+ ions co-doped; Dy3+/Sm3+ ions co-doped; Dy3+/Tm3+ ions co-doped; Tm3+/Dy3+/Sm3+ ions tri-doped systems), which is beneficial to tune the emission colors. Under the 360 nm excitation, the CIE coordinates of Tm3+/Dy3+/Sm3+ ions tri-doped samples are close to the standard equal energy white light illumination (x=0.333, y−0.333). With an increasing in Sm3+ ions concentration, blue and green emissions decrease gradually while red emission increases. In addition, the energy transitions among Tm3+, Dy3+, and Sm3+ ions are discussed in detail. The phenomenon is reasonably interpreted based on the analysis of the luminescence lifetime.