Insight into the Thermal Quenching Mechanism for Y3Al5O12:Ce3+ through Thermo luminescence Excitation Spectroscopy
Insight into the Thermal Quenching Mechanism for Y3Al5O12:Ce3+ through Thermo luminescence Excitation Spectroscopy
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DOI：
10.1021/acs.jpcc.5b08828
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发表时间：
2015-11-05
影响因子：
3.7
通讯作者：
Tanabe, Setsuhisa
中科院分区：
文献类型：
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作者：
Ueda, Jumpei;Dorenbos, Pieter;Tanabe, Setsuhisa
Y3Al5O12(YAG)：Ce3+是白光LED(w-LED)中应用最广泛的荧光粉，因为它具有很强的蓝光吸收和高效的黄色发光，并具有较高的稳定性和热猝灭温度，这是大功率w-LED在极端工作条件下所必需的。高的发光猝灭温度(类似于600K)已经得到了很好的确定，但令人惊讶的是，温度猝灭的机理尚未阐明。在这份报告中，我们通过测量不同温度下的热释光(TL)激发光谱来研究热电离作为这种猝灭过程的原因的可能性。在室温下的热释光(TLE)谱中，没有Ce3+：5d(1)带(最低激发5d能级)。然而，在对应于发光猝灭起始温度的573K的TLE光谱中，在450 nm附近观察到了Ce3+：5D(1)激发产生的TLE带。根据我们的观察，我们得出结论：YAG：Ce~(3+)的高温发光猝灭是由热电离引起的，而不是由热激活跃迁到4f基态引起的。分析了Ce3+的SD态在能带图中相对于导带的位置，证实了这一结论。
Y3Al5O12(YAG):Ce3+ is the most widely applied phosphor in white LEDs (w-LEDs) because of strong blue absorption and efficient yellow luminescence combined with a high stability and thermal quenching temperature, required for the extreme operating conditions in high-power w-LEDs. The high luminescence quenching temperature (similar to 600 K) has been well established, but surprisingly, the mechanism for temperature quenching has not been elucidated yet. In this report we investigate the possibility of thermal ionization as a cause of this quenching process by measuring thermoluminescence (TL) excitation spectra at various temperatures. In the TL excitation (TLE) spectrum at room temperature there is no Ce3+:5d(1) band (the lowest excited 5d level). However, in the TLE spectrum at 573 K, which corresponds to the onset temperature of luminescence quenching, a TLE band due to the Ce3+:5d(1) excitation was observed at around 450 nm. On the basis of our observations we conclude that the luminescence quenching of YAG:Ce3+ at high temperatures is caused by the thermal ionization and not by the thermally activated cross over to the 4f ground state. The conclusion is confirmed by analysis of the positions of the Sd states of Ce3+ relative to the conduction band in the energy band diagram of YAG:Ce3+.