Multichip LED Modules With V-Groove Surfaces for Light Extraction Efficiency Enhancements Considering Roughness Scattering

Although multichip light-emitting diode (LED) modules are becoming popular in high-power lighting applications, better light extraction efficiency is always desirable in the industry. In this paper, V-grooves fabricated by the low-cost dicing process have been utilized on the top face of the multichip LED module to enhance the output power. An analytical model including the consideration of surface has been established by using a fractal theory. The combined finite difference time domain and ray tracing method has been used to simulate the light extraction enhancement considering the surface roughness scattering effects. The results show 12% enhancements in the experiments when the measured surface roughness of the V-groove has RMS roughness of 0.25 μm, which is in good agreement with the simulation result of 13.7%. The multichip LED models have been applied in indoor downlight systems and it is found that the luminous efficiency has been enhanced by 9.6% under a current of 350 mA (5.8 W) when compared with multichip LED modules without V-grooves.