Boosting the 1540 nm near-infrared luminescence of Er3+ doped double perovskites via cross-relaxation and energy transfer

Abstract

Rare earth (RE) doped lead-free double perovskites (DPs) are potential near-infrared (NIR) light source materials due to their non-toxicity, simple preparation and low price. In this work,Cs2Ag0.1Na0.9BiCl6 DPs were chosen as matrix materials and different RE ions (Eu3+/Yb3+/Tb3+) were co-doped with Er3+ ions to study the effective ways to further enhance the NIR luminescence of Er3+ at 1540 nm in DPs. It found that double-doping (Eu–Er, Tb–Er, and Yb–Er) can improve the 1540 nm emission of Er3+ in DPs through cross-relaxation (CR) and energy transfer (ET), respectively. For tri-doped samples (DPs-Yb-Eu-Er and DPs-Yb-Tb-Er), the CR process between the Eu3+ (Tb3+) and Er3+ ions and the ET process from Yb3+ to Er3+ ions enhance synergically the luminescence of Er3+ at 1540 nm. Under excitation at 365 and 980 nm, the luminescence enhancement of DPs-Yb-Eu-Er at 1540 nm is 6.2 and 45 times, respectively, compared with that of DPs-Er. At the excitation of 365 nm, the photoluminescence quantum yield (PLQY) of DPs-Yb-Eu-Er is 18.2%, which is the maximum efficiency recorded reported so far for micron level DPs. Finally, DPs-Yb-Eu-Er was embedded into a polymethyl methacrylate (PMMA) polymer matrix to form a NIR light-emitting diode (LED) device. Good night vision imaging and tissue penetration experiments were performed under the irradiation of this NIR LED. This work provided a new method for the design of RE doped lead-free DPs with effective NIR emission.