Tunable white light by varying excitations in yttrium alumino bismuth borosilicate glasses co-doped with Dy3+-Eu3+ for cool WLED applications

Abstract Yttrium alumino bismuth borosilicate (YABiBS) glasses doped with RE 3+ ions (Eu 3+ , Dy 3+ , Dy 3+ - Eu 3+ ) have been synthesized via standard melt quenching technique and their emission properties were investigated. Optical analysis of these glasses is characterized by absorption and luminescence. XRD spectra reveal that these glasses have amorphous nature. The absorption spectra of these co-doped glasses consist five bands of Dy 3+ which are assigned to 6 H 15/2  →  6 F 3/2 (750 nm), 6 F 5/2 (796 nm), 6 F 9/2 (1085 nm), 6 F 11/2 (1264 nm) , 6 H 11/2 (1677 nm) and another four bands of Eu 3+ assigned to 7 F 0  →  5 L 6 (393 nm) Meza-Rocha et al. (2017) [5], 5 D 2 (464 nm), 7 F 6 (2097 nm) , and 7 F 1  →  7 F 6 (2202 nm). It is also witnessed a broad band having electronic transition 1 S 0  →  1 P 1 is due to Bi 3+ ions. Optical band gaps, nephelauxetic ratio, and bonding parameters are discussed by using optical absorption data. Eu 3+ single doped glasses show five emission bands, with the n-UV excitation wavelength 393 nm, in which characteristic feature red emission (612 nm) is recognized with transition (Meza-Rocha et al., 2017 [5])D 0  →  7 F 2 . At the same time, Dy 3+ single doped glasses illuminated with the excitation wavelength of 385 nm shows their known natural emissions blue (481 nm) and yellow (574 nm), having transitions 4 F 9/2  →  6 H 15/2 and 4 F 9/2  →  6 H 13/2 respectively. Emission for co-doped glasses Dy 3+ -Eu 3+ are excited with the different selected ultraviolet wavelengths such as 464 nm, 392 nm, 385 nm, 363 nm, and 348 nm. It can be observed that tunable emission from both the ions (Dy 3+ , Eu 3+ ) from orange reddish emission to white emission. The energy transfer from Dy 3+ to Eu 3+ is manifested by the quadrupole-quadrupole mechanism, which is confirmed by Inokuti-Hirayama (I H) modal based on lifetime decay curves. Also, the efficiencies and probabilities of energy transfer are determined based on the results of decay curves. The CIE color coordinates of DE1.0 glass with the excitation 348 nm gives x, y coordinates as (0.332, 0.342) which confers the good white emission. CCT value for this glass is around 5520 K shows that useful for cool WLED applications.