High emission quantum yield Tb3+-activated organic-inorganic hybrids for UV-down-shifting green light-emitting diodes

Abstract

Solid-state light-emitting diodes (LEDs) are driving the lighting industry towards efficient and environmentally friendly lighting and displays. Current challenges encompass efficient and low-cost down-shifting phosphors with tuned emission colors. Green light lies on the low-loss optical transmission window in plastic optical fibers and plays a special role in the regulation of the human and plant circadian rhythms. Moreover, green-emitting phosphors may suppress the “green gap” found in semiconductor-based LEDs. In this work, a UV-photostable green-emitting complex, Tb(NaI)3(H2O)2, with NaI = nalidixic acid (1-ethyl-1,4-dihydro-7-methyl-4-oxo-1,8-naftiridine-3-carboxylic acid), was incorporated into tripodal organic-inorganic hybrid materials. The hybrid hosts boost the absolute emission quantum yield from ≈ 0.11 (isolated complex) to ≈ 0.82 (doped hybrid), which is the largest value reported for Tb3+-based hybrid phosphors. A green-emitting LED was fabricated by coating a near-UV LED (365 nm) with a Tb3+-activated organic-inorganic hybrid having pure-green-colored light with Commission International de l'Eclairage color coordinates and an efficacy value of (0.33, 0.59) and 1.3 lm W–1, respectively.