Design of inclined omni-directional reflector for sidewall-emission-free micro-scale light-emitting diodes

Micro-scale light emitting diode (mu LED) reduces the front self-luminous display area by orders of magnitude, which brings the increase of sidewall emission and the resulting crosstalk between adjacent sub-pixels of displays. Reflector coating on the mu LED's sidewall is effective for the collection and utilization of side emission light. However, the existing multilayer periodic dielectric mirrors are undesirable for all angular reflection. In this paper, an omni-directional reflector (ODR) is designed for the mu LED display pixel to effectively utilize light leakage from the sidewall emission and improve the total light extraction efficiency (LEE). The designed ODR is insensitive to the angular distribution of the incident light, and has the capability to reflect the light reaching the mu LED's sidewall into the escape cone for front emission. By introducing the two-dimensional finite-difference time-domain method, the mu LED laminated structure is established to analyze the sidewall emission with an optimal inclination angle. By introducing the ODR for the inclined mu LED pixel, the overall LEE can be increased by 2.24 times and the sidewall emission is reduced by 99.6% compared with conventional vertical mu LEDs. Simulation and experimental results are in good agreement. The proposed ODR is expected to achieve the increase of LEE and sidewall-emission-free mu LED displays.