Revealing Eu3+-doped yttrium pyrogermanate as a soft UV excitable phosphor: retaining the pros of the commercial phosphor and compensating for the cons

• Published in: New journal of chemistry 2022-09, Vol.46 (37), p.17755-17766
• Main Authors: Tyagi, Adish, Nigam, Sandeep, Vats, B G, Sudarsan, V, Majumder, C, Kaiwart, R, Poswal, H K, Jagannath, Tyagi, A K
• Format: Article
• Language: English
• Subjects: Absorption; Efficiency; Electron energy; Emission; Near ultraviolet radiation; Phosphors; Photoluminescence; Quantum efficiency; Solid state; Ultraviolet radiation; X ray photoelectron spectroscopy; Yttrium; Yttrium oxide
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d2nj03374g

A paucity of red emitting phosphors efficiently excitable in the soft UV region has been a huge barrier in solid state lighting applications from the combination of a near-UV LED exciting chip and down conversion phosphors. The present work unveils the competence of an Eu-doped yttrium pyrogermanate phosphor (Y2Ge2O7:Eu) efficiently excitable in the soft-UV region. Single phase Y2Ge2O7:Eu with 2–10% Eu content was prepared by conventional solid-state reaction and thoroughly characterized using XRD, FTIR, RAMAN and XPS techniques. To examine the potential of the Y2Ge2O7:Eu phosphor, its photoluminescence behavior was compared with standard commercial red phosphor Y2O3:Eu. Remarkably, the results reveal that Y2Ge2O7:Eu retains the pros of the commercial phosphor and compensates for its cons. Whilst the emission profile, decay lifetime and internal quantum efficiency of Y2Ge2O7:Eu are almost identical to those of Y2O3:Eu, its Eu-incorporation capacity without concentration quenching is as high as 10% contrary to 5–6% of Y2O3:Eu owing to the less dense distribution of Y-sites in the Y2Ge2O7 host. High loading of Eu-content makes Y2Ge2O7:Eu suitable for high contrast displays. Whereas the Y2O3:Eu phosphor has negligible absorption efficiency in the soft UV region, the Y2Ge2O7:Eu phosphor has its maximum absorption efficiency around 390 nm nicely aligned with the emission of near UV LED chips. DFT calculations revealed that relatively deeper positioning of the Y2Ge2O7 valence electron energy states and associated covalency are decisive for its demonstration of competing performance. Successful dispersion of Y2Ge2O7:Eu inside a polymer matrix further endorses its potential towards future flexible device applications.