Spectral shifting and NIR down-conversion in Bi3+/Yb3+ co-doped Zn2GeO4
Spectral shifting and NIR down-conversion in Bi3+/Yb3+ co-doped Zn2GeO4
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DOI：
10.1039/c4tc01242a
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发表时间：
2014-01-01
影响因子：
6.4
通讯作者：
Wondraczek, Lothar
中科院分区：
文献类型：
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作者：
Gao, Guojun;Peng, Mingying;Wondraczek, Lothar
我们报告了通过近红外下转换 (DC) 光致发光 (PL) 对 Yb3+-Bi3+-共掺杂 Zn2GeO4 进行光谱修改。 UV-A 辐射的能量降档 (DS) 通过高带隙半导体 Zn2GeO4 的本征发光以及活性 Bi3+ 中心发生。同时，这两种物质都充当 Yb3+ 的敏化剂，将其激发区域强烈扩展至大约 500 nm。在没有 Bi3+ 的情况下，Zn2GeO4 在 UV 区域的带间吸收导致 PL 类似于 475-625 nm。掺杂 Yb3+ 会在协作 DC 过程中启动从捕获缺陷态到两个相邻 Yb3+ 离子的能量转移，从而产生类似于 1000 nm 的 Yb3+ 相关光电发射。在Zn2GeO4:Yb3+中引入Bi3+极大地将吸收带扩展到可见蓝色区域。然后，能量也通过协同直流发生从 Bi3+ 到 Yb3+ 的转移。结果，观察到绝对 Yb3+ 相关 PL 强度的强烈增加。这使得能够超高效地收集 UV-A 到可见辐射以进行能量转换过程。
We report on spectral modification through NIR down-conversion (DC) photoluminescence (PL) in Yb3+-Bi3+-co-doped Zn2GeO4. Energetic downshifting (DS) of UV-A irradiation occurs via intrinsic luminescence of the high-bandgap semiconductor Zn2GeO4 as well as via active Bi3+ centres. In parallel, both species act as sensitizers for Yb3+, strongly extending its excitation region to similar to 500 nm. In the absence of Bi3+, band-to-band absorption of Zn2GeO4 in the UV region results in PL at similar to 475-625 nm. Doping with Yb3+ initiates energy transfer from trapped defect states to two neighbouring Yb3+ ions in a cooperative DC process, resulting in Yb3+-related photoemission at similar to 1000 nm. The introduction of Bi3+ into Zn2GeO4:Yb3+ greatly extends the absorption band to the visible blue region. Then, energy transfer also occurs through cooperative DC from Bi3+ to Yb3+. As a result, a strong increase in the absolute Yb3+-related PL intensity is observed. This enables ultra-efficient harvesting of UV-A to visible radiation for energy conversion processes.