During the operation of an LED array, its thermal and optical performances are always not equal to the superposition of the individual LED's characteristics because of a significant thermal coupling effect between the arrays. Based on this, this paper proposes an electrical–photo-thermal model, with considering both junction temperature and luminous flux, to predict the both the thermal and optical performances of LED arrays operated under different currents, case temperatures, and lighting methods. The junction temperature and luminous flux of a single LED operating under different driving currents and case temperature conditions are firstly collected to establish the luminous flux response surface model of a single chip. Then it is used to predict the luminous flux of an array, whose junction temperature is predicted using both thermal coupling matrix (TCM) and numerical models. Experiments verify the luminous flux of the LED array under different operation conditions and show that the proposed electrical–photo-thermal modeling can be used to predict the thermal and optical parameters of LED arrays with 95 % accuracy. Thus, it is effective for the fast prediction of the junction temperature and luminous flux of large LED systems with array structures, i.e. intelligent automotive lightings and displays.

Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce³⁺) single crystal phosphor (SCP) exhibits high internal quantum efficiency (IQE) and excellent thermal conductivity and stability. Such properties are promising in high-power laser-excited white lighting applications. However, YAG:Ce³⁺ SCP usually shows low luminous flux and color rendering index (CRI, Ra) when excited by a transmissive laser. In this study, a self-designed three-integrating sphere system was established to characerize the optical performances of YAG:Ce³⁺ SCP palates under both the reflective and transmissive 455 nm blue laser excitations. Next, its luminous and color rendering properties under transmissive laser excitation were improved by surface roughening treatment and sintering of a CaAlSiN₃:Eu²⁺ (CASN:Eu²⁺) phosphor-in-borate glass (PiBG) layer. The results revealed that: (1) When the YAG:Ce³⁺ SCP was excited by blue laser, its forward luminous flux was considerably lower than the backward one; (2) Under transmissive excitation, its luminous flux rolled up with the maximum increase rate of 109.19% when the averaged roughness (R_a) increased from 0.35 to 5.40 μm; (3) After sintering the CASN:Eu²⁺ PiBG layer on the roughening YAG:Ce³⁺ SCP, its luminous flux, CRI increased by 31.48% and 117.14%, and its color fidelity index (CFI, R_f) reached up to 82 under the transmissive 3.03 W blue laser excitation.