###### Abstract  
In this work, we investigated the luminous and melanopic efficiency of the radiation (LER/MER) performances of phosphor-converted LEDs (PC LEDs) with tunable spectral characteristics, namely peak wavelength, full width at half maximum (FWHM), and emission intensity. We constructed theoretical PC LED spectra based on the characteristics extracted from the database of IES TM-30-15, analyzed the relations between LER/MER and different spectral characteristics, and proposed spectral composition strategies at various correlated color temperatures (CCTs). Results showed that both MER and LER are linear with the FWHM of phosphor within the peak wavelength range in practical use, but the change in values by tuning emission intensity varies with spectral compositions. Hence, different spectral characteristics should be considered comprehensively. We further explored the trade-off between luminous and melanopic efficiency. Lowering the FWHM of phosphor and the intensity distribution of the blue LED can obtain higher LER and low circadian effect at lower CCT. As CCT increases, considering color rendering and the increase in the blue intensity distribution, besides reducing FWHM, tuning the peak wavelength close to the peak wavelength of V(\(\lambda\)) helps to reduce the circadian effect. These investigations provide optimization strategies for ideal melanopic and luminous performance of PC LED light sources.  
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chip-emitting and a phosphor-converted LED (PC LED) [1; 6; 7; 8]. Researchers have put forward trade-off strategies by boosting the LER with high color rendering properties [9; 10], whereas the study of melatonin suppression has revealed the impacts of spectral composition on human circadian rhythms [11; 12; 13], suggesting the inadequacy of traditional assessments of luminous efficacy and color rendering. Possible solutions to circadian lighting design were thus developed with RGBW LEDs [14; 15], based on the circadian action curve C(\(\lambda\)) and circadian stimulus model [16; 17]. On the other hand, studies also adopted the melanopic spectral efficiency function M(\(\lambda\)) in circadian lighting evaluation [12; 18]. Since the blue light hazard has been proven to be related to circadian rhythm, some research focused on the melatonin suppression effect at different short wavelengths, illumination intensities, and correlated color temperatures [19]. PC LEDs have been widely applied in practical use, but there are fewer studies on spectral optimization in circadian lighting for this type compared with RGB LEDs. Currently, spectral optimization work mainly focuses on synthesizing several specific monochromatic spectra and then selecting the optimal multi-channel combination under a series of lighting requirements. Hence, it is beneficial to work out their impacts on human circadian rhythms and corresponding spectral tuning strategies in daily use. More studies with respect to particular spectral characteristics and spectral construction are required for further spectral optimization and detailed spectral composition guidance.  
In this study, we focused on how different spectral characteristics simultaneously affect the luminous and melanopic efficiencies of PC LEDs, including peak wavelength, FWHM, and emission intensity. We found that the effect of each characteristic on LED performance varies with the spectral combination and should be considered comprehensively. Both MER and LER are linear with the FWHM of phosphor within the peak wavelength range in practical use. The maximum of LER at each FWHM corresponds to a similar peak wavelength. The change in values by tuning emission intensity varies with spectral compositions. Based on the investigated variation of MER and LER with tunable spectral characteristics, we provided feasible spectral composition guidance for PC LED performances, which contributes to the luminous and circadian performance optimization and evaluation from the perspective of spectral construction.