Phosphor‐in‐glass thick film formation with low sintering temperature phosphosilicate glass for robust white LED

Abstract

Phosphor-in-glass (PiG) thick film was fabricated on a borosilicate glass substrate using a conventional screen printing method and employing phosphosilicate glass to allow low-temperature sintering. The vehicle content and sintering temperature were optimized to form a thick film with a thickness of~50 lm. Commercial yellow (Y 3 Al 5 O 12 :Ce 3+ ) and red (CaAlSiN 3 :Eu 2+ ) phosphors were successfully incorporated within the glass matrix and then sintered at 550°C. Color-tunable white LEDs were achieved using the PiG thick films as a color converter by varying the glass to phosphor (GtP) ratio. The high luminous efficacy of up tõ 120 lm/W and high color rendering index of up to 89 in combination with the thermal quenching property prove the practical feasibility of the PiG thick films for high-power/high-brightness LED applications. K E Y W O R D S glass, luminescence, phosphors, thick films

Low-Yellowing Phosphor-in-Glass for High-Power Chip-on-board White LEDs by Optimizing a Low-Melting Sn-P-F-O Glass Matrix

“…This indicates that as the addition ratio of the phosphors increases, pores can be induced from the spaces created in the phosphor. These pores in PIG plates can reduce the light extraction efficiency because they induce optical scattering losses 8 . We therefore studied a sintering process involving the mixing of phosphor/glass frit and a high-viscosity solvent to carry the fluid melted glass to spaces created in the phosphor as well as a heat pressure process to reduce the number of pores.…”

“…However, the silicone binder used as a medium to disperse phosphors on the conventional LED package can cause serious problems, such as deterioration of the efficiency and longevity due to the yellowing phenomenon of silicone resins stemming from the highly accumulated energy of long-term heat radiation from the high-power pc-WLEDs 5–7 . During the last decade, several types of transparent glass ceramic matrixes have been developed as possible replacement candidates for silicone as a binder material to fabricate phosphor-in-glass (PIG) components that contain a certain amount of dispersed phosphor powder in a transparent glass ceramic medium (see Table 1) 8–19 . Although many papers have reported that PIGs have higher thermal conductivity levels and longer lifetimes than phosphor-in-silicone (PIS) binders, the luminous efficacy (LE) and color rendering index (CRI) of PIG-based pc-WLEDs remain inferior to those of conventional PIS-based pc-WLEDs.…”

Review—Phosphor Plates for High-Power LED Applications: Challenges and Opportunities toward Perfect Lighting

“…They found the glass composition for preventing recrystallization of CASN:Eu 2+ phosphor and successfully fabricated a wLED with the best combination of each phosphor, which had a CCT of 3789 K and a CRI of 93. Ahn et al 79 employed a PiG with a low sintering temperature based on the SiO 2 82 with the commercial YAG:Ce 3+ yellow phosphor. These red phosphors were proposed to solve the recrystallization problem.…”

Eu3+‐doped glass as a color rendering index enhancer in phosphor‐in‐glass

“…However, heat generated from high‐power LEDs may lead to yellowing, carbonization, and browning of the encapsulant and thus change the color temperature of the WLED and decrease its luminous efficacy. Different techniques have emerged to overcome these drawbacks, among these we find approaches such as glass‐ceramics, and phosphor in glass (PIG) . A PIG is formed by mixing a transparent glass powder with a phosphor material, and then the green body is sintered at a certain temperature, usually below 800°C.…”

“…Several approaches have been proposed to increase CRI value in PIGs, including randomly mixing glass and yellow phosphor with red phosphor, codoping YAG:Ce 3+ with Mn 2+ , embedding YAG in doped glass with Eu, creating alternated sections of yellow phosphor and red phosphor with circular section patterns, applying a thin red layer by screen printing, mixing both yellow and red phosphor and incorporate them on top of a glass via screen printing and recently creating alternated yellow and red sections by screen printing . CaAlSiN 3 :Eu 2+ (CASN:Eu 2+ ) is one of the most used phosphors with red emission .…”