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YAG:Ce3+ yellow phosphor are particularly used luminescent materials to produce white light in phosphor-converted white LED (pc-WLED). Surface coating of YAG phosphor is the main concern for desired optical performance of the phosphors. Many scholars conducted various experimental analysis on the surface coating of phosphors to improve yellow emission, but the theoretical explanation by which phosphor coating could help improving light efficiency has not yet been studied. In this paper, based on Mie theory, the optical constants such as scattering coefficient, absorption coefficient and asymmetry parameter of YAG:Ce3+ phosphor and YAG@SiO2 (YAG:Ce3+ phosphor surface coated with nano-SiO2 layer) were calculated. An optical configuration of chip scale packages (CSP) WLED was constructed by coupling YAG:Ce3+ or YAG@SiO2 phosphors with a LED laser. Based on the optical parameters calculated by Mie theory, the luminescent properties of YAG:Ce3+ and YAG@SiO2 WLED were simulated by Monte Carlo method. The results showed that a thin SiO2 coating layer on YAG phosphor result in an overall increase in luminous performances compared with original YAG WLED. The absorption coefficient of phosphor is the main concern affecting the light emission in WLED. Due to the fact that YAG@SiO2 possess higher 460 nm absorption coefficient , it could absorb more blue light than YAG, thereby it has a 1.2% higher conversion efficiency than YAG, finally the enhanced luminous efficiency of YAG@SiO2 WLED is obtained. The results obtained in this work provides a potential method in future WLED packaging designing.

Phosphor layer are essential in the application of phosphor-converted white light emitting diodes (pc-WLEDs). However, the conventional structure of red–green–blue (RGB) phosphor layers can cause severe re-absorption of blue light, resulting in low luminous efficiency and colour rendering index (CRI). In this paper, we fabricated a new WLEDs phosphor layer, which consisted of patterned RGB phosphor pixel arrays in a planar configuration, by the stencil printing technique. Optical simulation based on Monte-Carlo theory has been applied to assist designing the optimal pattern of the phosphor pixel arrays. By tuning the layout of the pixel arrays and the size of phosphor pixels, we achieved uniform output white light with high luminous intensity of 1.47 × 109 cd and CRI of 95.6, which are superior compared with the intensity of 1.11 × 109 cd and CRI of 93.5 obtained from WLEDs with conventional dispensing phosphor layer. Our newly-designed phosphor pixel-array layer possesses great potential for applications in advanced lighting and display devices with vast implications for industrial improvement in these research areas.

Phosphor layers are of vital importance for the development of advanced phosphor-converted light-emitting diodes (LEDs). However, owing to the fixed ratio of red-green-blue (RGB) phosphors, it has been difficult for the RGB phosphor layers with conventional structure to tune light emission colours. Herein, we have experimentally fabricated nine types of phosphor layers with patterned RGB pixel array, which consist of tuneable RGB ratio in a planar configuration. Moreover, we carried out optical simulation based on Monte-Carlo theory to assist in adjusting the light-emission colours and the corresponding chromaticity coordinates. The simulations were further verified by the experimental results via samples fabricated by the stencil printing technique. In accordance with the nine types of phosphor layers with patterned pixel arrays in various RGB ratios, we have finally obtained corresponding nine light-emission colours for the applications of LED light emission decoration. These designed advanced pixel-array phosphor layers demonstrate great potential for applications in decorated light emission and display devices with significant implications for industrial improvement in these research areas.