Color Conversion Materials for High‐Brightness Laser‐Driven Solid‐State Lighting

Abstract

Solid‐state lighting is advancing toward higher power, higher brightness, and smaller size to cope with the market competitiveness, and laser‐driven solid‐state lighting technology is springing up owing to its super‐high brightness and compactness. These developments put forward new requirements for color conversion materials (i.e., phosphors). Here, the state‐of‐art achievements in laser phosphors are summarized, and the topics of luminescence saturation, light extraction efficiency, and light uniformity encountered in laser lighting technology are discussed. Several typical types of color converters, such as single crystal, phosphor ceramics, phosphor‐in‐glass, phosphor films, and quantum‐well light‐emitting diodes, are comparatively overviewed and discussed. The cutting‐edge applications of high‐brightness white laser light in lighting, displays, healthcare, and communications are summarized. The challenges and outlook in laser‐driven solid‐state lighting and some empirical rules for designing novel laser phosphors are highlighted.

A Photostimulated BaSi2O5:Eu2+,Nd3+ Phosphor‐in‐Glass for Erasable‐Rewritable Optical Storage Medium

“…Especially, the long‐term repeatable UV‐laser write‐in process would cause slight shrinkage, visible colouration, coupled with an increase in brittleness . Alternatively, inorganic glass appears to be an optimizing candidate, which has been proven effective for high‐power LED/LD applications . In the experiment, a PiG composite was fabricated by co‐sintering the BaSi 2 O 5 :0.020Eu 2+ ,0.015Nd 3+ PSL phosphor with the commercial glass frit.…”

“…[52] Alternatively, inorganic glass appears to be an optimizing candidate, which has been proven effective for high-power LED/LD applications. [53][54][55] In the experiment, a PiG composite was fabricated by co-sintering the BaSi 2 O 5 :0.020Eu 2+ ,0.015Nd 3+ PSL phosphor with the commercial glass frit. The base glass shows glass transition temperature (T g ) of 372°C ( Figure S8a, Supporting Information) and the coefficient of thermal expansion (CTE) of 0.23 × 10 −6 K −1 (Figure S8b evidencing the combination of BaSi 2 O 5 :0.020Eu 2+ ,0.015Nd 3+ particles with glass matrix.…”

Unique Design Strategy for Laser‐Driven Color Converters Enabling Superhigh‐Luminance and High‐Directionality White Light

“…[5] Obviously, blue LDs have inherent advantages of high optical flux density and low etendue, and are appreciated for small luminaire designs. [6,7] At the same time, it brings new challenges to the design of color converters to accommodate the distinguishing features of LDs. [8][9][10][11] Firstly, the phosphor materials must withstand long-term high flux density laser irradiations and dissipate the generated heat within the small laser spot.…”

“…Third, the blue LDs have a lower beam divergence, that is, the perpendicular and parallel beam divergence angles of blue LD are typically 45° and 9°, respectively, while the blue LEDs usually show a Lambertian emission with a full‐width half‐maximum (FWHM) of 120° . Obviously, blue LDs have inherent advantages of high optical flux density and low etendue, and are appreciated for small luminaire designs . At the same time, it brings new challenges to the design of color converters to accommodate the distinguishing features of LDs .…”

Limitations to emission spot size in laser lighting

“…When the phosphor material is heated by the incident blue laser light, the efficiency drops. This drop is termed thermal quenching and has been investigated in several phosphor materials as limiting the luminous flux under high intensity laser illumination [6,[13][14][15][16].…”