A matching method to reduce the distribution of optical and electrical properties of white light-emitting diodes

Phosphor-converted white light-emitting diodes (pc-WLEDs) inherently have large device-to-device variation in electrical and optical properties compared to conventional light sources. Wider variation means that a smaller proportion of products are appropriate for certain illumination or display applications. We present a method that reduces variation in chromaticity coordinates (x, y), luminous flux, Φ_lum, and forward voltage, V_f, simultaneously. In this method, two complementary LEDs form a pair matched quickly by a weighted matching algorithm. The matching results show that the device-to-device variance of x, y, Φ_lum, and V_f decrease by 96.0%, 93.7%, 79.3%, and 84.4%, respectively. The complementary devices also maintain low variance for all four properties under different currents ranging from 5 to 40 mA. A simulation reveals that the effect of the matching method is more effective with an increase of LED population.