Unique Color Converter Architecture Enabling Phosphor-in-Glass (PiG) Films Suitable for High-Power and High-Luminance Laser-Driven White Lighting

Abstract

As a next-generation high-power lighting technology, laser lighting has attracted great attention in high-luminance applications. However, thermally robust and highly efficient color converters suitable for high-quality laser lighting are scarce. Despite its versatility, the phosphor-in-glass (PiG) has been seldom applied in laser lighting because of its low thermal conductivity. In this work, we develop a unique architecture in which a phosphor-in-glass (PiG) film was directly sintered on a high thermally conductive sapphire substrate coated by one-dimensional photonic crystals. The designed color converter with the composite architecture exhibits a high internal quantum efficiency close to that of the original phosphor powders and an excellent packaging efficiency up to 90%. Furthermore, the PiG film can even be survived under the 11.2 W mm blue laser excitation. Combining blue laser diodes with the YAG-PiG-on-sapphire plate, a uniform white light with a high luminance of 845 Mcd m(luminous flux: 1839 lm), luminous efficacy of 210 lm W, and correlated color temperature of 6504 K was obtained. A high color rendering index of 74 was attained by adding a robust orange or red phosphor layer to the architecture. These outstanding properties meet the standards of vehicle regulations, enabling the PiG films with the composite architecture to be applied in automotive lighting or other high-power and high-luminance laser lighting.

A Thermally Robust La3Si6N11:Ce‐in‐Glass Film for High‐Brightness Blue‐Laser‐Driven Solid State Lighting

“…Figure d–g is the cross‐sectional SEM images of PiG films with different PtG ratios (i.e., P1G4, P2G3, P3G2, and P4G1) at a fixed thickness of ≈50 µm, demonstrating that all PiG films are tightly bonded to the CSP substrate. With the increase of the PtG ratio, more pores generate in the PiG films because the lower glass content prefers to produce more trapped air in the microstructure during the sintering process . The XRD patterns of the PiG film (P2G3‐50) in Figure h indicate a pure crystalline LSN:Ce phase (ICSD 248709) and an amorphous hump from the glass matrix.…”

“…The durability study was conducted with an accelerated aging test by treating samples under a saturated humidity condition at 200 °C as presented in the previous research, which is much harsher than the usually‐adopted D85 (85 °C and 85% RH) test. The optical performance of the PiG films under the high‐power laser excitation was measured in a transmissive configuration by using a sphere‐spectroradiometer system . The system consists of a high‐power blue laser source (LSR445CP‐FC‐48W, Lasever, Ningbo, China), an integrating sphere (30 cm in diameter, Labsphere Inc., USA), and a CCD spectrometer (HR4000, Ocean Optics, USA).…”

“…However, their applications in laser lighting have been limited due to the low thermal conductivity (≈1.0 W m −1 K −1 ). To overcome these shortcomings, a composite architecture, where a thin PiG film is sintered tightly on a high thermally conductive substrate (i.e., glass, sapphire, or aluminum) has been designed to enable PiGs to be applied in high‐power laser lighting …”

“…In our previous study, a YAG:Ce‐PiG film was sintered on a sapphire plate coated with 1D photonic crystals (1DPCs) . As the sapphire substrate has a high thermal conductivity of ≈30 W m −1 K −1 , the phosphor film could work under a laser power density of 11.20 W mm −2 and give a high luminous flux of 1839 lm.…”

“…In this study, we attempted to prepare the LSN:Ce‐PiG film on a 1DPCs‐coated sapphire by using the method reported in our previous study . The optical properties of the film under the blue laser irradiation were investigated.…”