The fabrication and optical property of WLED encapsulated with the graded-index fluorescent glass film

Abstract

The refractive index difference between the packaging material and the chip in white light-emitting diode (WLED) is a key factor to increase the light transmission efficiency. In this work, multilayer gradient index fluorescent glass film was fabricated through screen printing technology and low temperature sintering method, and used to encapsulate the blue chip. Combining the Monte Carlo simulation with experiment data, the ratio of YAG: Ce³⁺ phosphor to matrix glass, and the thickness of graded-index fluorescent coating film were determined. The refractive index of multilayer glass was controlled to change from 1.60 to 1.83 through adjusting the Bi₂O₃ concentration. It is found that gradient refractive index fluorescent glass coating can effectively improve the transmittance of the packaging material and increase the luminous efficiency of WLED. In addition, encapsulating WLED with gradient refractive index fluorescent glass in place of organic materials can extend the life of WLEDs. This work revolves around the effect of gradient refractive index fluorescent glass coating on WLED performance and effectively improves its luminous efficiency.