Analytical/Experimental Hybrid Approach Based on Spectral Power Distribution for Quantitative Degradation Analysis of Phosphor Converted LED

Lumen depreciation and color quality change of phosphor-converted LED (pc-LED) are caused by the combination of various degradation mechanisms including chip, phosphor layer, and packaging material degradations. We present an analytical/experimental hybrid procedure to quantify the effect of each mechanism on pc-LED degradation. A mathematical model based on the spectral power distribution (SPD) is proposed after defining each degradation parameter. The model decomposes effectively the SPD change caused by the degradation into the contributions of individual degradation mechanisms. The model is implemented using the SPDs of a pc-LED with conformally coated phosphor, obtained before and after 9000 hours of operation. The analysis quantifies the effect of each degradation mechanism on the final values of lumen, CCT, and CRI.