Characterization, packaging, and optical model of single-primary color phosphor thin films and LEDs

Abstract

Blue, green, and red phosphor thin films (PTFs) used for NUV LED were prepared by hot pressing method. The excitation spectrums of PTFs have broadband absorption characteristics owing to the 4f7 → 4f65d transition of Eu2+; the emission peaks are 445 nm, 520 nm, and 627 nm, respectively. The phosphor conversion efficiency (PCE) gradually increases and finally remains unchanged with phosphor mass fractions because of absorption saturation effect. Different color LEDs are packaged by NUV chips and PTFs; spectral decomposition and data fitting methods are used to achieve the fitting of the relationship between the phosphor mass fraction and the emission light intensity of the NUV chip and phosphor. The double Gaussian model is used to express the spectral power distribution (SPD) of a single-primary color LED and compare it with the measured results. White LEDs (WLEDs) were prepared by two methods, the first is the combination of multi-LEDs, the second is NUV chip pumps three-color-mixed phosphor directly. Experimental results showed that the WLEDs prepared by first method with the light color parameters of CCT = 5342 K, LER = 274 lm/W, show small parameter difference of ΔCCT = 24 K, ΔLER = 15 lm/W, NCC = 98.94% compared with the calculated results. The WLEDs prepared by second method with the light color parameters of CCT = 5292 K, LER = 263 lm/W shows a 4.0% decrease in LER.