Synthesis And Luminescence Mechanisms Of BaZnOS Phosphors

The white-light-emitting diodes(LEDs)have attracted extensive application due to their long lifetime,high luminescence efficiency,low power consumption,and environmental friendly characteristics.The commercial WLEDs are fabricated by a combination of a blue-emitting InGaN chip coated with yellow-emitting phosphors such as cerium-doped yttrium aluminum garnet(YAG:Ce).However,this kind of WLED shows a poor color rendering index(Ra<80)for the scarcity of red emission.To solve this problem,two approaches are proposed.One is achieved by using a near-ultraviolet(NUV)chip coated with red,green,and blue phosphors.And the other one is to develop a single-component white-light-emitting phosphor.BaZnOS,as a semiconductor,shows a good chemical and thermal stability,which suggest that it may act as a development potential of phosphor matrix material.Moreover,the compound containing two kinds of different metal ions:Ba2+ and Zn2+,which can produce a wealth of phosphor materials with different properties by doping some other ions.1.Synthesis and luminescence mechanism of BaZnOS matrixThe BaZnOS matrix is synthesized through different methods,and its luminescence mechanism is also discussed.The luminescence property of the BaZnOS matrix is different with the change of the contentof carbon impurities.The reasons for this phenomenon may be the sulphur vacancy defects V**s and carbon impurity defects Ci formed in the BaZnOS matrix.When the content of carbon impurity defects are too many,the sample mainly shows blue-green emitting centered at 506 nm because of the Ci defect plays a leading role.Otherwise,the sample mainly shows red emitting peaked at 637 nm due to the sulphur vacancy defects Vs play a leading role.2.Luminescence property of BaZnOS:Cue+,Mn2+,Ga3+ phosphorThis paper has studied the influence on the luminescence property of BaZnOS:Cu2+,Mn2+ phosphor by trying doping a variety of transition metal ions.Ga3+ is used as a sensitizer to improve the absorption intensity of blue-green light.As a result,the absorption band of the BaZnOS:Cu+,Mn2+,Ga3+ phosphors effectively widen which covers the range from 225 to 550 nm and also expands the application range of the solar energy and luminescence efficiency.The experimental results suggest that the sample might be a promising phosphor for white LED and green-turn-red(GTR)electroluminescent materials.3.Synthesis and luminescence property of BaZnOS:Cu2+ phosphorNon-rare earth phosphors Cu2+-doped BaZnOS were prepared by a conventional high-temperature solid state reaction.When excited by 330 nm and 377 nm,all CIE color coordinates of the BaZni-xOS:xCu2+samples were found to locate in the white region.It had been found that the nominal composition BaZn0.9996OS:0.04%Cu2+ is the optimal composition for single-phased white-light phosphor.And the corresponding CIE(0.313,0.325)of this sample is close to the ideal white light(0.33,0.33)under 377 nm excitation.The luminescent mechanisms Cu2+-doped BaZnOS were discussed in detail.It may be the recombination of the matrix luminescence and the characteristic luminescence of the Cu2+ ions.4.Sensitized luminescence of BaZnOS:Eu2+ phosphorsThe BaZnOS:Eu2+ phosphor synthesized through carbonthermal reduction method has a weak absorption band in blue area.In the paper,Ce3+ ion is used as a sensitizer,after concentration optimizing,the results show that the optimal doping concentration of Ce3+ ion is 0.6 mol%.Due to the energy transfer between Eu2+ and Ce3+,the luminescence intensity of BaZnOS:Eu2+ phosphors obviously improve through the Ce3+ ion sensitization.