Red-shifting and boosting the emission of NaScP2O7:Cr3+ via efficient energy transfer for information encryption and anti-counterfeiting

Highly-efficient near-infrared (NIR) phosphors with long-wavelength emission (>900 nm) are crucial to broaden the potential applications of NIR phosphor-converted light-emitting diodes (pc-LEDs) in practical scenarios. In this study, we synthesized an NIR phosphor, Cr³⁺-activated NaScP₂O₇ with emission centered at 920 nm and a full width at half maximum (FWHM) of 208 nm. Nevertheless, the phosphor yields an internal quantum efficiency (IQE) of 9.8 %, owing to severe non-radiative relaxation. By introducing Yb³⁺ co-dopant into NaScP₂O₇:Cr³⁺, the role of Cr³⁺ changes from an activator to a sensitizer, enabling efficient Cr³⁺-Yb³⁺ energy transfer (ET). The resulting NaScP₂O₇:Cr³⁺,Yb³⁺ exhibits a characteristic Yb³⁺ emission peaking at 1005 nm. Notably, the IQE of the co-doped phosphor is significantly enhanced to 58.9 %, attributed to the suppression of Cr³⁺ non-radiative relaxation and the efficient sensitization of Yb³⁺ emission through ET. Benefiting from the intensive short-wavelength infrared emission (SWIR), the phosphor demonstrates versatile applications in anti-counterfeiting and information encryption.