Study On Luminescence Properties Of Perovskite Ca_1-xLa_2x/3TiO₃ System Doped With Rare Earth Ions Eu³⁺,Dy³⁺,Sm³⁺

With the development of science and technology in the era,solid-state lighting has now reached the fourth stage,which is dominated by white light-emitting diodes.The emission performance of ultraviolet-excited white LEDs largely depends on the three primary color phosphors:red,green and blue.And now commercial red phos-phor Y2O2S:Eu3+,has shown strong excitation peaks in the near-UV region,but it also has low absorption efficiency.Therefore,the development of high-luminescence red phosphor,which could be excited effectively under the near-UV region,is essen-tial and urgent.On the other hand,one of the widely used commercial WLED is yellow phosphor Y3Al5O12:Ce3+in combination with a blue-emitting chip(InGaN)Unfortunately,the absence of the red composition leads to some drawbacks such as high correlated color temperature,poor color rendering index and a strong ther-mal quenching,which limiting its wider range of applications.Therefore,when the phosphor lacks effective red light emission,we can supplement its red part by doping other rare earths,thereby solving the problemIn this thesis,the characteristics of perovskite Ca1-xLa2x/3TiO3 system doped with rare earth ions Eu3+,Dy3+and Sm3+were investigated in detail.The results were as follows(1)For perovskite Ca1-xLa2x/3TiO3 system single doped with rare earth ions Eu3+,it was found that the phosphors have good absorption at 396 nm in the near-ultraviolet region and show satisfactory emitting at 591 and 616 nm in the red light region.When the Eu3+ ions doping concentration is 1 mol%,the red emission intensity of Ca0.9La0.067TiO3:Eu3+was strongest.Therefore,Ca0.9La0.067TiO3 was selected as the main research object in this part,and its Eu3+ions optimal doping concentration was 5 mol%.The color coordinates of Ca0.9La0.067TiO3:5 mol%Eu3+were(0.636,0.364),which approached the location of commercial red phosphor and ideal red light.For Ca0.9La0.067TiO3:5 mol%Eu3+phosphor has a higher IQE compared with the Y2O2S:Eu3+ commercial phosphor(IQE:35%)and reached as high as 83.7%.The synthetic phosphor Ca0.9La0.067TiO3:5 mol%Eu3+was fabricated with commercial blue and green phosphors BaMgAl10O7:Eu2+ and Sr2SiO4:Eu2+,respectively.The electroluminescence spectrum shows correlated color temperature(CCT)and color rendering index(Ra)were 6295 K and 94.4,which were better than the white LEDs currently in commercial use:YAG:Ce3+(CCT=7760 K,Ra<65).Therefore,the Ca1-xLa2x/3TiO3 system is expected to be red light component of WLED devices.(2)For Ca1-xLa2x/3TiO3 doped with Dy3+,under the excitation of near-ultraviolet light at 388 nm,blue and white light emission was observed at 482 and 573 nm,respectively.After calculating the correlated color temperature,it belongs to the category of cool white light.For Ca1-xLa2x/3TiO3 doped with Sm3+,under 404 nm excitation wavelength,it generates three yellow and red emissions,which are located at 565,601 and 648 nm,respectively.Therefore the perovskite Ca1-xLa2x/3TiO3 sys-tem doped with Dy3+and Sm3+could be used to manufacture blue and yellow-red LED,respectively.To synthetic a phosphor that can emit warm white light,per-ovskite Ca1-xLa2x/3TiO3 system used to co-doped with Dy3+and Sm3+ions.The phosphors achieve conversion of cool white and warm white light by varying the concentration of Dy3+and Sm3+ions.The temperature-dependent emission spec-tra indicated that Ca1-xLa2x/3TiO3:Dy3+,Sm3+ exhibited good thermal stability.The fabricated phosphor Ca1-xLa2x/3TiO3:Dy3+,Sm3+ had CCT and Ra values of 6064 K and 71,respectively.They had better performances than commercial white LEDs.Therefore,Ca1-xLa2x/3YiO3.Dy3+,Sm3+ can be a promising candidate for near-ultraviolet excited WLEDs.