Research On High-Power Phosphor-Converted White LED/LD Packaging And Its Opto-Thermal Performances

In the context of global energy shortage,semiconductor solid-state light source has gradually replaced the traditional light sources owing to its advantages of high light efficiency,low power consumption,long lifetime,and environmental friendly,which leads the continuous improvement of national energy conservation and environmental protection ability.With the increasing demand in the field of lighting and display,solid-state light source technology is developing towards high power and high density,resulting in multi-chip integrated white light-emitting diode（LED）and next-generation white laser diode（LD）.Currently,the white LED/LD usually use phosphor-converted white technology in which the blue chips excite the yellow phosphor to form white light.However,the traditional organic phosphor materials（silicone or epoxy resin）are prone to the fracture of functional group dissociation under high-power chip excitation,which leads to the problems of the aging and carbonization of organic material and the thermal quenching of phosphor.These problems seriously affect the opto-thermal performances of high-power white LED/LD.Therefore,this thesis studies the high-power phosphor-converted white LED/LD packaging and its opto-thermal performances.The inorganic color converter of phosphor-in-glass（PiG）was proposed to replace the organic phosphor color converters.In order to improve the color rendering and luminescence stability of white LED/LD,the spectral compensation mechanism,color rendering and heat conduction enhancement mechanism,and luminescence stability were studied,which can promote the development and practical application of high-power white LED/LD technology.The main research contents include:1)The preparation process of PiG by screen printing and low-temperature sintering was proposed.The packaging structure of PiG-based high-power white LED/LD was discussed,in which the remote packaging structure was used for PiG-based white LED,and the transmission and reflection packaging structures were used for PiG-based white LD.The optical performance evaluation indexes of white LED/LD were analyzed.2)The spectral compensation methods of PiG-based white LED were proposed to improve the color rendering of white LED,including liquid quantum dot（QD）integrated PiG,UV-excited moth-eye microstructured PiG,and broadband PiG.The red liquid QD was integrated with yellow PiG to compensate for the red spectral region,and the excellent warm white light(R_a=93.9,R₉=97.7,and R₁₃=98.1)was achieved for the liquid QD integrated PiG-based white LED.The moth-eye structure was used to reduce the total reflection loss of PiG surface,and the packaged white LED increased the light efficiency of 20.96%under the premise of ensuring the color quality.The broadband PiG was prepared to recover the cyan spectral gap,and the white LED obtained full-spectrum white light with the color rendering index（CRI）greater than 95.3)The heat conduction enhancement methods of PiG-based white LED were proposed to improve its luminescence stability,including high heat-conducting PiG and QD-PiG-sapphire.The sapphire substrate has high thermal conductivity,which provides an effective heat dissipation channel for the PiG film.Compared with the traditional PiG and the phosphor-in-silicone（Pi S）,the working temperature of heat-conducting PiG is reduced by31°C（～30%）and 46°C（～39%）,respectively.The QD-PiG-sapphire was prepared by stacking the QD film on the PiG-sapphire.Due to the high thermal conductivity of PiG-sapphire,the working temperature of QD film was reduced and the thermal stability of QD-PiG-sapphire packaged white LED was improved.4)The high-brightness white LD technology of“blue LD+PiG”was proposed,including transmissive white LD and reflective white LD.In the transmissive white LD,a multi-color PiG was used to control the spectrum and improve the color quality of transmissive white LD,and a high color rendering index laser white light(R_a>85,R₉>80,and R₁₃>89)was obtained.A double-sided sapphire structure was designed to provide double-sided heat dissipation channel for PiG film and improve the thermal stability of white LD.In the reflective white LD,an aluminized reflective PiG was designed to improve photon reflection and extraction originating from the high reflectance of aluminum film,and the light efficiency of white LD reaches 115 lm/W.The PiG film was directly prepared on an aluminum substrate with high thermal conductivity,and the aluminum-based PiG still maintained the low working temperature under the excitation of high-power blue LD,which improved the thermal dissipation and luminescence stability of white LD.