White light emitting diode by using α-Ca2P2O7:Eu2+, Mn2+ phosphor

Abstract

The α-Ca2P2O7:Eu2+, Mn2+ phosphors show two emission bands peaking at around 416 (blue) and 600nm (orange), originating from the allowed f-d transition of Eu2+ and the forbidden T14-A16 transition of Mn2+, respectively, under near ultraviolet (UV) excitation at 400nm. Spectroscopy and fluorescence lifetime measurements demonstrate that energy transfer from Eu2+ to Mn2+ performs with transfer efficiency as high as 65% for Mn2+ concentration of 12mol%. The authors have fabricated a white light emitting diode (LED) through the integration of GaN near-UV chip and two phosphor blends (α-Ca2P2O7:Eu2+, Mn2+ blue-orange phosphor and Ba2SiO4:Eu2+ green phosphor) into a single package. The white LED shows color rendering index of 78, luminescent efficiency of 9lm∕W, and low color point variation against forward-bias currents.

Efficient and tuneable photoluminescent boehmite hybrid nanoplates lacking metal activator centres for single-phase white LEDs

“…The long-lived contribution (SD42.00 ms) is characterized by an emission decay curve described by a bi-exponential function ( Supplementary Fig. 20 and Supplementary Table 5) ascribed to a first-order process followed by a second-order phosphorescence component typical of F-centres [6][7][8][9][10][11][12] . The lifetime value measured for the benzoate-related triplet states ( Supplementary Fig.…”

“…Recently, solid-state phosphor white lightemitting diodes (WLEDs) have received considerable attention. WLED devices exhibit extra-long lifetime, excellent thermal resistance, higher luminous efficiency and lower power consumption compared to mercury-based fluorescent lamps [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] . There are at least three methods to generate white light in WLEDs: (i) the combination of three primary red, green and blue LEDs (RGB-WLED); (ii) the blue chip (450-470 nm)-pumped WLED (BLUE-WLED) and (iii) the near-ultraviolet chip (350-420 nm)-pumped WLED (ultraviolet WLED) [2][3][4] .…”

“…However, due to the reabsorption of light within the multicomponent phosphors, non-uniformity of luminescent properties with colour altering and a decrease of luminous efficiency are generally observed 2,20 . For these reasons, an ultraviolet-pumped WLED based on a single layer of a full-colour-emitting phosphor would be highly advantageous, promising very small colour variations, high CRI and low cost 5,6,[8][9][10][11][12][13]18,21,22 . Nevertheless, actual downconverting phosphors involves the doping or co-doping of inorganic compounds mostly with lanthanide ions such as europium(III) 5,6,9,13,18,21,22 , whose scarcity [23][24][25] and supply disruption is a noticeable concern.…”

“…Ultraviolet-pumped WLEDs have huge potential because they are easy to manufacture, the white light emission is only due to the downconverting phosphors, they exhibit a low colour point variation as a function of the forward-bias currents and they have superior temperature stability [5][6][7][8][9][10][11][12] . Moreover, as the human eyes are insensitive to ultraviolet radiation, the white colour is independent of the pumping LED and thickness of the phosphor layer 15 .…”

A novel phosphor for glareless white light-emitting diodes

“…There have been many reports describing the development of phosphors [7][8][9][10][11][12][13][14][15][16] for violet chips, which have an external quantum efficiency that is intrinsically higher than that of blue chips [17][18][19] . A pc-LED with a violet chip generates white light only from the luminescence of the phosphors.…”