Tetravalent manganese-doped lithium meta-silicate red-emitting phosphors for LED applications: structural and luminescence properties

Abstract

In this paper, different concentrations of tetravalent manganese-activated lithium meta-silicate red-emitting phosphors, namely Li₂SiO₃:xMn⁴⁺ (x = 0.01, 0.02, 0.03, 0.04 and 0.05 mol), have been prepared by the solid-state reaction method at 950 °C. The structural, thermal, morphological, and optical properties of the sintered phosphors were characterized by powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), raman, UV-Visible and photoluminescence (PL) spectra. Excitation and emission spectra are used to study optical characteristics, which match well with the commercially visible region. The red emission bands for Li2SiO3:0.02Mn⁴⁺ peak at approximately 642 nm (λ_ex = 425 nm) and 717 nm (λ_ex = 475 nm), respectively due to the spin-forbidden ²E → ⁴A₂ transition. The doping concentrations of xMn⁴⁺ in the Li₂SiO₃ host were investigated, and the correlations between Mn⁴⁺ doping concentration and luminescence intensity were examined. The Commission Internationale de l'Eclairage (CIE) chromatic coordinate graph confirmed the emission color observation in the red region, showed an excellent color purity (CP). In addition, the quantum efficiency (QE) of Li₂SiO₃:Mn⁴⁺ phosphors reached up to 70.51%. The investigation shows that synthesized Li₂SiO₃:Mn⁴⁺ phosphors are beneficial for red Light-Emitting Diodes (LEDs) used in solid-state lighting.

KEYWORDS:

• Li₂SiO₃:xMn⁴⁺
• photoluminescence
• red-emitting phosphors
• Raman spectra

Acknowledgements

The corresponding author, Dr. Ishwar Prasad Sahu, would like to acknowledge the Science and Engineering Research Board (SERB), New Delhi, Government of India for funding the FTIR Spectrophotometer (CRG/2018/004139). This instrument is used for the IR spectroscopic analysis of the prepared sample from the study. Priya Barik and Ishwar Prasad Sahu: Investigated and designed the whole research, conceptualized, synthesized all the samples and collected experimental data, Data plotting, write the manuscript, reviewed, edited and formatted and edited the manuscript corresponding to the journals. Aksh Kumar Verma, Pradeep Dewangan, Manorama Sahu, Anjali Mehto: manuscript editing, thorough analysis and revised the articles’ review. Ravinder Kumar, Vinod Kumar: Recorded temperature-dependent emission spectra and proposed many good suggestions.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors state that analyzed and relevant data of synthesized materials, which are included and described in the manuscript will be freely available to researchers and scientists who are working for research and social welfare.

Additional information

Funding

The corresponding author Ishwar Prasad Sahu, is thankful to University Grant Commission of India (UGC) for the UGC-BSR Start-up Fellowship (No. F.30-420/2018 (BSR), dated 23/10/2018), Government of India.