Controlled energy transfer has been found to be one of the most effective ways of designing tunable and white photoluminescent phosphors.Utilizing host emission to achieve the same would lead to a new dimension in the...Controlled energy transfer has been found to be one of the most effective ways of designing tunable and white photoluminescent phosphors.Utilizing host emission to achieve the same would lead to a new dimension in the design strategy for novel luminescent materials in solid state lighting and display devices.In this work,we have achieved controlled energy transfer by suppressing the host to dopant energy transfer in La_(2)Hf_(2)O_(7):Eu^(3+)nanoparticles(NPs)by co-doping with uranium ions.Uranium acts as a barrier between the oxygen vacancies of the La_(2)Hf_(2)O_(7) host and Eu^(3+)doping ions to increase their separation and reduce the non-radiative energy transfer between them.Density functional theory(DFT)calculations of defect formation energy showed that the Eu^(3+)dopant occupies the La^(3+)site and the uranium ion occupies the Hf^(4+)site.Co-doping the La_(2)Hf_(2)O_(7):Eu^(3+)NPs with uranium ions creates negatively charged lanthanum and hafnium vacancies making the system highly electron rich.Formation of cation vacancies is expected to compensate the excess charge in the U and Eu co-doped La_(2)Hf_(2)O_(7) NPs suppressing the formation of oxygen vacancies.This work shows how one can utilize the full color gamut in the La_(2)Hf_(2)O_(7):Eu^(3+),U6+NPs with blue,green and red emissions from the host,uranium and europium,respectively,to produce near perfect white light emission.展开更多
基金support from the National Science Foundation under CHE(award#1952803 and#1710160)the United States-India Education Foundation(USIEF)and the Institute of International Education(IIE)for his Fulbright Nehru Postdoctoral Fellowship(award#2268/FNPDR/2017).
文摘Controlled energy transfer has been found to be one of the most effective ways of designing tunable and white photoluminescent phosphors.Utilizing host emission to achieve the same would lead to a new dimension in the design strategy for novel luminescent materials in solid state lighting and display devices.In this work,we have achieved controlled energy transfer by suppressing the host to dopant energy transfer in La_(2)Hf_(2)O_(7):Eu^(3+)nanoparticles(NPs)by co-doping with uranium ions.Uranium acts as a barrier between the oxygen vacancies of the La_(2)Hf_(2)O_(7) host and Eu^(3+)doping ions to increase their separation and reduce the non-radiative energy transfer between them.Density functional theory(DFT)calculations of defect formation energy showed that the Eu^(3+)dopant occupies the La^(3+)site and the uranium ion occupies the Hf^(4+)site.Co-doping the La_(2)Hf_(2)O_(7):Eu^(3+)NPs with uranium ions creates negatively charged lanthanum and hafnium vacancies making the system highly electron rich.Formation of cation vacancies is expected to compensate the excess charge in the U and Eu co-doped La_(2)Hf_(2)O_(7) NPs suppressing the formation of oxygen vacancies.This work shows how one can utilize the full color gamut in the La_(2)Hf_(2)O_(7):Eu^(3+),U6+NPs with blue,green and red emissions from the host,uranium and europium,respectively,to produce near perfect white light emission.
