Luminescence Properties Of Bi³⁺ And Rare Earth Ion Doped Ba₂Y (BO₃)₂Cl Phosphors And Mechanism Research

Bi³⁺and rare-earth ions co-doping phosphor has an important application in many fields,such as solid-state lighting,solar cells and temperature sensing.Ba₂Y?BO₃?₂Cl hosts presents the low prepared temperature and the excellent physical and chemistry stability.Due to the variety of sites,Ba₂Y?BO₃?₂Cl phosphors were used as an excellent host material.Therefore,the synthesis of phosphor doped with photo-active ions,such as Bi³⁺and rare earth ions,has important scientific significance and application value.In this paper,Bi³⁺and rare-earth ions(Eu³⁺,Yb³⁺?Yb³⁺/Er³⁺)co-doping phosphors were synthesized by using the conventional solid-state method,and the luminescence characteristics and mechanism of the samples were systematically investigated.Novel Ba₂Y?BO₃?₂Cl:Bi³⁺,Eu³⁺phosphors were fabricated,and their photoluminescence properties were investigated.Three difference luminescence peaks located at the 366,410 and490 nm were observed in the single Bi³⁺doped Ba₂Y?BO₃?₂Cl phosphor under the excitation of ultraviolet light attributed to three various Bi³⁺sites occupied in the Ba₂Y?BO₃?₂Cl host.By tuning the excitation wavelength from three various Bi³⁺sites,the tunable luminescence properties were obtained.The energy transfer from Bi³⁺at various sites to Eu³⁺were observed in the Ba₂Y?BO₃?₂Cl:Bi³⁺,Eu³⁺phosphors by an electric dipole-dipole interaction.The tunable and white luminescence was obtained by changing the Eu³⁺concentration or excitation wavelength.The light-emitting diodes with the white light emission were constructed by coupling Bi³⁺and Eu³⁺co-doped Ba₂Y?BO₃?₂Cl phosphors with the UV chip,which indicated that the Bi³⁺and Eu³⁺co-doped Ba₂Y?BO₃?₂Cl phosphors can act as a promising candidate for the UV converted WLEDs.Ba₂Y?BO₃?₂Cl:Bi³⁺,Yb³⁺quantum cutting phosphors were prepared,and their quantum cutting luminescence and energy transfer mechanism were investigated.The visual emission of Bi³⁺was observed ranging from 350 to 650 nm,which is attributed to the ³P₁?¹S₀ transition of Bi³⁺.The near infrared emission ranging from 950 to 1100 nm is due to the ²F_7/2?²F_5/2 transition of Yb³⁺.The cooperative energy transfer mechanism from the Bi³⁺to Yb³⁺in Ba₂Y?BO₃?₂Cl:Bi³⁺,Yb³⁺phosphor was investigated,and their cooperative energy transfer process could be expressed as the ³P₁?²F_5/2+²F_5/2.The maximum total quantum efficiency was about 170.2%,which suggested the Bi³⁺and Yb³⁺co-doped Ba₂Y?BO₃?₂Cl phosphors can act as a promising candidate for the silicon solar cells.It is well known that the upconversion?UC?peak of ⁴S_3/2?⁴I_15/2 transition of Er³⁺is close to that of ²H_11/2?⁴I_15/2 transition.The UC emission splitting of Er³⁺caused by coordination fields of host result in it is difficult to confirm which the transition(⁴S_3/2?⁴I_15/25/2 or ²H_11/2?⁴I_15/2)is responsible for the splitting UC emission peak.In this work,the Yb³⁺,Er³⁺co-doped Ba₂Y?BO₃?₂Cl UC phosphor was synthesized by using the conventional solid-state method.Upon the 980 nm excitation,the UC luminescence peaks located at 524,540,551,565,662,677and 683 nm were observed.The 524 and 540 nm UC emission intensity was increased,while the551 and 565 nm UC emission intensity decreased with the increasing of temperature from 323 K to 573 K,which is attributed to the phonon-assisted population inversion from the ⁴S_3/2/2 level to the ²H_11/21/2 level.The temperature dependence of UC emission spectra demonstrated that the 524and 540 nm luminescence peaks are from ²H_11/2?⁴I_15/2 transition,and 551 and 565 nm peaks are attributed to the ⁴S_3/2?⁴I_15/2 transition.Temperature sensing property were characterized by the UC luminescence intensity ratio of the ²H_11/2?⁴I_15/2 transition to ⁴S_3/2?⁴I_15/2 transition,and the five various temperature sensitivity parameters can be obtained due to the splitting of upconversion emissions.The Yb³⁺,Er³⁺co-doped Ba₂Y?BO₃?₂Cl phosphor has potential application as non-contact temperature sensor.