Cool white light and tunable multicolor emission from Tb3+/Dy3+ co-activated glasses under different excitations for WLEDs

Abstract

A set of co-doped (Tb3+/Dy3+) lithium zinc borate (LZB) glasses were developed by melt quenching. The structural evaluation was performed for synthesized glassy matrices. The Dy3+ and Tb3+ individually doped glasses exhibit intense yellow and green luminescence bands at 575 nm (4F9/2 → 6H13/2) and 543 nm (5D4→7F5), respectively. The sensitization effect of Dy3+ on Tb3+ was analyzed by increasing the Tb3+ content with respect to the optimum Dy3+ content (0.5 mol%) in Dy3+/Tb3+. The spectral overlay of Dy3+ luminescence and Tb3+ absorption profiles, Dy3+/Tb3+ PL spectra under different excitations 352, 362, 376, and 385 nm, shortening decay lifetimes of Dy3+ in Dy3+/Tb3+ co-activated glasses, energy transfer (ET) parameters, chromaticity coordinates and their corresponding correlated temperatures all help to explain ET from Dy3+ to Tb3+. At 385 nm of Dy3+ excitation, the optimized co-activated (0.5Dy3++1.0Tb3+):LZB glass displays cool white light emission. The non-radiative ET from Dy3+ to Tb3+ is dominated by electric dipole–dipole interaction and its ET efficiency was calculated to be 63%. At the same time, reverse ET from Tb3+ to Dy3+ was also analyzed. The shift in color coordinates from dominant yellow to greenish-yellow, green and white light emission suggests that Dy3+/Tb3+ co-activated LZB glasses can be a potential candidate for UV converted multicolor and white light emitting devices.