Visible-to-infrared quantum cutting by phonon-assisted energy transfer in YPO4:Tm3+, Yb3+ phosphors

• Published in: Physical chemistry chemical physics : PCCP 2012-01, Vol.14 (19), p.6974-698
• Main Authors: Zheng, Wei, Zhu, Haomiao, Li, Renfu, Tu, Datao, Liu, Yongsheng, Luo, Wenqin, Chen, Xueyuan
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c2cp24044k

Quantum cutting (QC) of one visible photon into two infrared ones has been reported for the lanthanide ion couple (Tm 3+ , Yb 3+ ) in a variety of host lattices. The mechanism responsible for QC was assumed to be a cooperative energy transfer (ET) process from Tm 3+ to two Yb 3+ ions, however, no solid evidence was presented. Herein we report visible-to-infrared QC for (Tm 3+ , Yb 3+ ) in YPO 4 phosphors. The ET process from the excited 1 G 4 level of Tm 3+ to Yb 3+ was investigated in detail by means of optical spectroscopy. By monitoring the steady-state photoluminescence (PL) and PL decay of the intermediate 3 F 4 level of Tm 3+ as a function of the Yb 3+ concentration, we demonstrated the QC of one incident blue photon into one near-infrared emitting photon at 1004 nm from Yb 3+ and simultaneously into one mid-infrared emitting photon at 1791 nm from Tm 3+ , rather than two emitting photons from Yb 3+ . It was revealed that such visible-to-infrared QC was induced by phonon-assisted ET instead of cooperative ET as previously reported. This kind of QC phosphors may have potential as solar spectral converters to enhance the external quantum efficiency in multi-junction solar cells based on narrow band-gap semiconductors such as Ge, PbS or In 1− x Ga x N. A comprehensive survey of the visible-to-infrared quantum cutting and energy transfer mechanism involved in Tm 3+ -Yb 3+ co-doped YPO 4 phosphors has been performed, revealing the quantum cutting of one incident blue photon into one NIR emitting photon of Yb 3+ and one mid-infrared (MIR) emitting photon of Tm 3+ through phonon-assisted energy transfer.