Sn2+/Mn2+ co-doped germanate glass with quasi-sunlight spectrum visible-emission and its high-quality w-LED application

Light sources with the spectrum distribution approaching the sunlight, even in the visible range, are preferred. Up to now, sunlight simulator is still a great challenge to the scientists. In this work, the Sn2+/Mn2+ doped germanate glasses with the emission near to the sunlight spectral distribution in the visible wavelength region were developed, and the corresponding applications in w-LEDs were demonstrated. The spectral properties including excitation and emission characteristics, concentration quenching, fluorescence dynamics for Sn2+ and Mn2+ single-doped germanate glasses were studied. It is found that both Sn2+ and Mn2+ single-doped glasses can be effectively excited by broadband ultraviolet and subsequently generate broadband visible emissions. However, the emission from each of single-doped glasses does not cover full visible wavelength range. Fortunately, it is found that the lack of the red spectral component in the broadband visible emission of Sn2+ single-doped glass can be compensated by the broadband red emission of Mn2+. On that base, the Sn2+/Mn2+ co-doped germanate glasses were fabricated and studied. Broadband emission covering full visible range, good luminescence thermal stability and excellent chromatic performance were realized in the co-doped glasses by optimizing concentration and engineering energy transfer. Finally, a prototype w-LED was assembled by the Sn2+/Mn2+ co-doped germanate glass and a 310 nm LED chip. The prototype w-LED reveals the sunlight-like visible spectrum, good color coordinates (0.380, 0.371), low correlated color temperature (CCT) of 3811 K and high color rendering index of 95.3, indicating that the Sn2+/Mn2+ co-doped germanate glasses are promising candidate to develop high performance w-LED.