Enhancement of flip-chip white light-emitting diodes with a one-dimensional photonic crystal

A design for a one-dimensional photonic crystal (1D PhC) based on thin-film optics is proposed to improve the light extraction efficiency of phosphor-converted flip-chip white-light-emitting diodes (LEDs). The 1D PhC thin film consisting of alternating layers of TiO2 and SiO2 is added between a phosphor layer and sapphire substrate of the LEDs. Monte Carlo simulation method is introduced to analyze performance of the proposed LEDs with a 1D PhC. Results show that the light extraction efficiency is higher than that of conventional LEDs by 16%, and the correlated color temperature becomes lower, below 4000 K. These improvements are attributed to the efficient extraction of backscattered light from the phosphor layer by using the 1D PhC thin film.