Ruixin Li

Optical performance improvement of phosphor-in-glass based white light-emitting diodes through optimized packaging structure.

To improve the optical performance of multi-component phosphor-in-glass (PiG) based white light-emitting diodes (WLEDs), we proposed an optimized packaging structure, which is a combined structure of a patterned PiG with a crater-type lens. The patterned PiG yields a red phosphor circle surrounded by a yellow phosphor concentric ring. Comparison simulations and experiments between the conventional mixed structure, patterned structure, and proposed structure were conducted. Compared with the mixed structure and patterned structure, the luminous efficacy of the proposed structure is increased by 19.3% and 10.7% at the driving current of 350 mA, respectively. Furthermore, the deviation of the correlated color temperature (CCT) of the patterned PiG is reduced from 906 to 129 K by the crater-type lens at the average CCT of 4100 K. The results demonstrate that the proposed packaging structure can improve the luminous efficacy and angular color uniformity (ACU) of a PiG-based WLED simultaneously.

Luminous efficacy enhancement of ultraviolet-excited white light-emitting diodes through multilayered phosphor-in-glass.

To enhance the luminous efficacy of ultraviolet-excited white light-emitting diodes (WLEDs), a novel packaging structure that is based on a multilayered red, green, and blue (RGB) phosphor-in-glass (PiG) was proposed. The RGB PiG was prepared by screenprinting and low temperature sintering, and the effects of different configuration orders of RGB phosphor layers on the optical performance of WLEDs were studied. Compared with the conventional mixed-RGB PiG, the luminous efficacy of WLEDs packaged by the multilayered PiG with the order of R-G-B is increased by 8.2% at the driving current of 500 mA, and the corresponding correlated color temperature (CCT) and color rendering index (CRI) are 2984 K and 86.8, respectively. Moreover, the WLEDs packaged by multilayered G-R-B PiG yield the highest luminous efficacy of 27.19 lm/W at the expense of color quality, which is still an acceptable warm light, with a CCT of 3326 K and a CRI of 84.2.

Luminous Properties and Thermal Reliability of Screen-Printed Phosphor-in-Glass-Based White Light-Emitting Diodes

This paper systematically investigates the luminous properties and thermal reliability of phosphor-in-glass (PiG)-based white light-emitting diodes (WLEDs). The PiG was prepared by introducing yellow YAG:Ce3+ phosphor embedded with borosilicate glass through screen-printing and low-temperature sintering. The effects of sintering temperature, phosphor content, and phosphor layer thickness were studied, and then the optimized PiG was achieved. This PiG-based WLED module yields a luminous efficacy (LE) of 114 lm/W, a correlated color temperature of 5524 K, and a color rendering index of 69 at the driving current of 700 mA. Furthermore, after thermal aging test at 200 °C for 500 h, the photoluminescence intensity of PiG is only reduced by 4.3%, which is much lower than the conventional phosphor-in-silicone (PiS) of 26.2%. The LE losses of PiG-based and PiS-based WLED modules are 4.2% and 12.1% after thermal aging of 1000 h at 100 °C, respectively. The aging results show that the proposed PiG exhibits superior thermal stability characteristic, which promises the excellent thermal reliability for PiG-based WLEDs.

Thermal resistance investigation of ceramic substrates for high-power light-emitting diodes packaging

Thermal resistance model of packaged light-emitting diode (LED) samples was proposed to investigate the thermal performances of different ceramic substrates. The thermal resistances of four metallized ceramic substrates were measured by using thermal transient tester. Consequently, the thermal resistances of TFC-Al₂O₃, DPC-Al₂O₃, DBC-Al₂O₃ and DPC-AlN are 8.09 K/W, 7.05 K/W, 4.78 K/W, and 1.57 K/W, respectively. Experimental results also demonstrate that fabrication process and ceramic materials can greatly affect the thermal performances of ceramic substrate.

Enhancement in light extraction of white leds using micro-cone patterned phosphor-in-glass

Phosphor-in-glass (PiG) patterned with micro-cone arrays, which can be fabricated by photolithography and inductively coupled plasma dry etching methods, is proposed to enhance light extraction efficiency (LEE) of white light-emitting diodes (LEDs) package. The effects of microstructure arrays on the LEE of LEDs are investigated by optical simulations and experiments. Optical performance of the LED package with microstructure patterned PiG is compared with that of flat PiG. Simulation results reveal that the truncated cone microstructure can increase the LEE by 12.3%. Experimental results also demonstrate that the enhancement of luminous efficiency of white LED reaches up to 9.7% with the inverted truncated cone microstructure.

Development of RGB phosphor-in-glass for ultraviolet-excited white light-emitting diodes packaging

To obtain high CRI and improve color quality of white light-emitting diodes (WLED), a red, green and blue (RGB) phosphor-in-glass (PiG) was developed for ultraviolet (UV)-excited WLED packaging. RGB PiG was fabricated by screen-printing of glass paste and low temperature sintering. The effects of mass ratio and concentration of RGB phosphor on the optical performances of UV-excited WLED were investigated. UV-excited WLED with luminous flux, color rendering index(CRI), Correlated Color Temperature(CCT) of 118.8lm, 86.0 and 5406K, respectively, are achieved by using RGB PiG with optimized phosphor ratio (R:G:B) at 1.45:3:1, concentration at 0.4 and three times printing with the total thickness of 90 μm.

Multi-layered red, green, and blue phosphor-in-glass for ultraviolet-excited white light-emitting diodes packaging

To enhance the optical performance of ultraviolet (UV)-excited white light-emitting diodes (WLEDs), a novel packaging structure using multi-layered red, green, and blue (RGB) phosphor-in-glass (PiG) was proposed. The RGB PiG was fabricated by screen-printing and low temperature sintering. Comparison experiments between the conventional mixed-RGB structure and proposed packaging structure were conducted. Consequently, Compared with the mixed-RGB PiG, the luminous flux of WLEDs packaged by the multi-layered PiG with the order of R-G-B increases by 8.8% at the driving current of 500 mA, and the corresponding correlated color temperature (CCT) and color rendering index (CRI) are 4065 K and 85.6, respectively.

High-power white LED packaging using phosphor-in-glass and its thermal reliability

This paper proposed a yellow YAG:Ce3+ based PiG for high-power white light-emitting diode (WLED) packaging, and its thermal reliability was systematically investigated. The PiG was fabricated by introducing yellow YAG:Ce3+ phosphor embedded with borosilicate glass through screen-printing and low-temperature sintering. The thermal aging tests of PiG were carried out and compared with the conventional phosphor-in-silicone (PiS). After aging of 200°C for 500 h, the photoluminescence (PL) intensity of PiG is only reduced by 4.3%, which is much smaller than the PiS of 26.2%. In addition, The PiG-based WLEDs achieve the stable optical performance under the various aging conditions of PiG. The aging results show that the prepared PiG exhibits superior heat resistance characteristic, which induces the excellent thermal reliability for PiG-based WLEDs.