Comprehensive investigations of near infrared downshift and upconversion luminescence mechanisms in Yb3+ single-doped and Er3+, Yb3+ co-doped SiO2 inverse opals

摘要

Comprehensive investigations of near infrared (NIR) downshift and visible upconversion luminescence (UCL) mechanisms were carried out for Yb3+ single-doped and Er3+, Yb3+ co-doped SiO2 inverse opals under excitation at 256, 378, 520 and 980 nm. NIR emission at 976 nm from the Yb3+-O2- charge transfer state and UCL emission at 500 nm due to the cooperative emission of two Yb3+ ions were observed in SiO2: Yb3+ inverse opal upon excitation at 256 and 980 nm, respectively. The cooperative UCL of two Yb3+ ions was suppressed due to the photon trap created by the photonic band gap. For the SiO2: Er3+, Yb3+ inverse opals, NIR emission of Yb3+ at 976 nm and of Er3+ at 1534 nm were observed upon excitation at 256, 378 and 520 nm, respectively. Upon excitation at 378 and 520 nm, the 976 nm NIR emission of Yb3+ does not arise from (H-2(11/2)/S-4(3/2)) + 2Yb(3+)(F-2(7/2)) -> Er3+(I-4(15/2)) + 2Yb(3+)(F-2(5/2)) traditional quantum cutting. The NIR emission of Yb3+ at 976 nm may be due to the Er3+(H-2(11/2)) + Yb3+(F-2(7/2)) -> Yb3+(F-2(5/2)) + Er3+(I-4(11/2)) cross-relaxation energy transfer process upon excitation at 520 nm. The NIR emission of Yb3+ at 976 nm may arise from the cross-relaxation energy transfer of Er3+((4)G(11/2)) + Yb3+(F-2(7/2)) -> Yb3+(F-2(5/2)) + Er3+(F-4(9/2)) and Er3+(F-4(9/2)) + Yb3+(F-2(7/2)) -> Yb3+(F-2(5/2)) + Er3+(I-4(13/2)) upon excitation at 378 nm.