Designing ultra-highly efficient Mn2+-activated Zn2GeO4 green-emitting persistent phosphors toward versatile applications

Developing highly efficient green-emitting phosphors is very significant because human eyes are sensitive to green spectral region. Herein, Mn2+-activated Zn2GeO4 phosphors, which can emit bright green light with an ultrahigh internal quantum efficiency of 98.5%, were prepared by a solid-state reaction technology in ambient atmosphere. At 323 nm irradiation, the emission spectrum shows a narrow band centered at 534 nm, which is ascribed to the 4T1 → 6A1 transition of Mn2+, with a full width at half maxima of 49.5 nm. Through monitoring the temperature-dependent photoluminescence emission intensity and decay time of Mn2+, we explored the thermometric properties of the resultant compound and found maximum relative sensitivities of Zn2GeO4:0.02Mn2+ phosphor are 4.90% K−1 and 0.74% K−1, respectively. Furthermore, green afterglow phenomenon is observed in the designed phosphors, and its mechanism is verified by discussing the thermoluminescence. Because of the excellent luminescence behaviors, various multimode luminescent patterns for information encryption are designed, including anticounterfeiting and fingerprint identification. Furthermore, using the prepared Zn2GeO4:0.02Mn2+ as green-emitting components, a white-light-emitting diode with suitable color coordinates, high color rending index (>90), and low correlated color temperature (5,000–6,000 K) was fabricated. These results demonstrate that Mn2+-activated Zn2GeO4 phosphors are multifunctional green-emitting components for optical thermometry, anticounterfeiting, fingerprint detection, and solid-state lighting applications.