Enriched upconversion emission and electrical properties of Er3+/Yb3+/Mn: ZnWO4 phosphors for display and anti-counterfeit applications

Abstract

The upconverting codoped/tridoped ZnWO₄: Er³⁺/Yb³⁺/Mn materials have been synthesized for structural, electrical and optical studies. The X-ray diffraction (XRD) investigation confirms the highly crystalline monoclinic phase of the prepared material. The elemental mapping indicates complete incorporation of the raw ingredients in the host. Charge transfer band (CTB) is observed between the Mn⁴⁺ and O²⁻ ions in the interval 239–282 nm of the Diffuse Reflectance Spectra (DRS). Some characteristic absorption bands of Mn³⁺ ion due to ⁵E^/ →⁵E^// transition is also observed in the region 806–908 nm of the DRS spectra. We have also reported the Raman and Fourier transform of Infra-red (FTIR) vibrations of the optimized sample in the present investigation. The temperature dependant EPR spectra infers cation vacancies in the host matrix. The XPS study confirms the mixed state of Mn⁴⁺ and Mn³⁺ ion in the host material. The CIE spectra and photometric calculations shows that these high colour purity phosphors may be explored to design cool LEDs. The investigation of electrical parameters advocates display applications in the temperature region 30 °C to 100 °C of the prepared material. The anti-counterfeit application is also demonstrated in the present study.