## 3 Results  
### Investigated Practical PC LEDs and Extracted Spectral Characteristics  
A total of 119 relative spectral power distributions of commercial PC LEDs provided in the database of IES TM-30-15 were adopted, from which the spectral characteristics were extracted, as shown in Figure 2. The spectral compositions in practice were divided into two groups according to whether the emission intensity ratio of blue LED to phosphor (B:Y ratio) was greater than 1. Under these two conditions, B:Y ratios range from 1:0.44 to 1:0.97, and from 0.33:1 to 0.99:1, respectively. We found that the mean peak wavelength (\(\lambda_{1}\), 449.67 \(\pm\) 4.81 nm and 450.95 \(\pm\) 4.19 nm) and FWHM (\(\Delta\lambda_{1}\), 23.91 \(\pm\) 2.92 nm and 26.11 \(\pm\) 4.02 nm) of blue LEDs are concentrated. However, the mean peak wavelength and FWHM of phosphor (\(\lambda_{2}\) and \(\Delta\lambda_{2}\)) differ greatly with the B:Y ratio. For PC LEDs of B:Y ratio \(>\) 1, \(\lambda_{2}\) and \(\Delta\lambda_{2}\) are 563.49 and 133.84 nm, respectively; for PC LEDs of B:Y ratio \(<\) 1, \(\lambda_{2}\) and \(\Delta\lambda_{2}\) are 604.08 and 149.27 nm, respectively, as shown in Figure 2. In addition, the asymmetric factor seems to be slightly different. Based on the extracted spectral characteristics above, we focused on the peak wavelength and FWHM of phosphor as well as the emission intensity ratio, since they are more adjustable in practical applications. Figure 1: The normalized spectra of photopic vision sensitivity V(\(\lambda\)) and melanopic efficiency M(\(\lambda\)). Luminous and Melanopic Efficiency Performance with Tunable Peak Wavelength, FWHM, and Emission Intensity  
In the subsequent spectral construction process, we constructed a series of spectra with Equations (1) and (2). MER and LER were then obtained with Equations (3) and (4). We analyzed the impacts of peak wavelength and FWHM of phosphor on MER and LER at a specific range of blue:yellow emission intensity ratios, as shown in Figure 3. Given that the practical spectrum of the blue LED exerts limited impacts outside of its small range of change, the peak wavelength and FWHM were fixed at 450 and 25 nm, respectively. We mainly adjusted the spectra of phosphor, in which the FWHMs varied from 100 to 200 nm. Different ranges of peak wavelengths were set according to a B:Y ratio > 1 or not. The B:Y ratio of the solid lines with square markers in Figure 3a,b is 1:0.7, and in Figure 3c,d corresponds to 0.6:1, with the peak wavelength ranging from 520 to 600 nm and from 520 to 620 nm, respectively. In addition, the filled area of light color in Figure 3a-d shows an influence from the variation of B:Y ratio, with the range of 1:(0.6-0.9) and (0.3-0.9):1, respectively. Compared with the practical spectra, the two asymmetric factors were set at 0.3 and \(-\)0.05. Figure 3 reveals the variation trends of MER and LER with tunable spectral characteristics. There are similar variation trends for MER and LER at different B:Y ratios, which are approximately linear with \(\Delta\lambda_{2}\), especially at \(\lambda_{2}\) below 600 nm. Figure 3a,c reveals that tuning \(\lambda_{2}\) is the most effective way to make a significant change in MER. With the increase in \(\lambda_{2}\), MER firstly decreases with \(\Delta\lambda_{2}\), and then turns to slightly increasing with it. The variation caused by \(\Delta\lambda_{2}\) is quite limited at \(\lambda_{2}\) above 560 nm. Moreover, adjusting the B:Y ratio hardly has an effect on MER, especially at the shorter part of \(\lambda_{2}\), but has a slight effect on the values of LER. In Figure 3b,d, LER linearly decreases with \(\Delta\lambda_{2}\) at \(\lambda_{2}\) below 600 nm. The subplots in Figure 3b,d indicate that no matter what the \(\Delta\lambda_{2}\) is, LER always peaks at \(\lambda_{2}\) of 545 nm with a B:Y ratio of more than 1, and varies to \(\lambda_{2}\) of 560 nm with a B:Y ratio less than 1, which forms a nearly symmetric distribution. Furthermore, LER has the greatest range of variation on these two axes as well.