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

Abstract 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 Lu 3 Al 5 O 12 :Ce 3+ phosphor‐in‐silica‐glass (LuAG:Ce‐PiSG) despite being sintered at 1250 °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.