In-plane Heat Transfer Enhancement of Phosphor Layer in Transmissive Laser-excited White Lighting

The phosphors in transmissive laser-excited white lighting play the core role of wavelength conversion, but they also act as the micro heat sources in the devices. Since the phosphors are normally wrapped by polymer packaging materials with extremely low thermal conductivity, the generated heat is hard to be dissipated in time, thus resulting in a sharp temperature rise of the phosphor layer during the working process, and even lead to thermal quenching and carbonization under high power scenarios. To tackle the above problem, an in-plane heat transfer enhancement strategy by forming hexagonal boron nitride (hBN) alignment in the phosphor layer using hot-pressing method is proposed in this paper. When the filling mass fraction of hBN reaches 7.5 wt%, the in-plane thermal conductivity of the phosphor layer increases by 89% compared with that of the traditional phosphor layer without hBN, and the corresponding maximum surface temperature decreases by 68.3 °C under the driving current of 800 mA. The in-plane heat transfer enhancement strategy proposed in this paper provides a powerful means to solve the local high temperature issue in the phosphor layer of transmissive laser-excited white lighting, and may hold great promise for the further application of white lighting devices.