Phosphor‐in‐Silica‐Glass: Filling the Gap between Low‐ and High‐Brightness Solid‐State Lightings

High-brightness phosphor-converted solid-state light (SSL) sources based on blue light-emitting diodes (LEDs) or laser diodes (LDs) will enable versatile optical applications other than general illumination. However, luminescence ceramics/crystals are too expensive for widespread use, while phosphor-in-glass converters suffer from low conversion efficiency at high-power-density excitation and poor chemical and thermal stabilities of low-melting glasses. Herein, an ultrathin interface (<50 nm) is reported in Lu3Al5O12:Ce3+ phosphor-in-silica-glass (LuAG:Ce-PiSG) despite being sintered at 1250 degrees C, endowing them with high internal quantum efficiency (>95%) and excellent stabilities. Combined experimental results and first-principles calculations reveal that the large formation energy of Si-Al point defects makes the undesired interfacial reaction between aluminate garnets and silica glass intrinsically suppressed. Phosphor-converted LEDs/LDs fabricated by LuAG:Ce-PiSG exhibit high luminous efficiency (195 lm W-1 @ 20 mA) and high brightness (1914 lm @ 13.4 W mm(-2)), approaching the performances of their ceramic counterparts. The results not only provide a way to balance the brightness and the price for SSL sources but also unleash the potential of silica glass as an inorganic matrix for emerging optical applications.