Figure 4 shows the forward I–V and the output power characteristics of the WB-AC LED I and II under DC source. It can be seen that the forward voltage at 2 mA is 131.9 V of WB-AC LED I and 116.7 V of WB-AC LED II, and the output power is 33 mW of WB-AC LED I and 44 mW of WB-AC LED II under the identical input power 1 W, respectively. It is found that the WPE of WB-AC LED I is lower than WB-AC LED II, even the radiation area of WB-AC LED I is larger than WB-AC LED II, which can be attributed to the current density of the rectified microchip is 896 A/cm2 in WB-LED I and 162 A/cm2 in WB-AC LED II under the identical input power 1 W, respectively. The higher current density of the rectified microchip in WB-AC LED I than WB-AC LED II causes the lower internal quantum efficiency and higher forward voltage that reduce the WPE of WB-AC LED I simultaneously. Figure 5 shows the time-variant input voltage and the output power characteristics of the WB-AC LED II driven by the AC 110 V source. The variance of the input AC source voltage is from 155 to –155 V and the frequency is 60 Hz. The WB-AC LED II radiates only after the input voltage higher than the sum of microchips’ threshold voltage, which is about 100 V, and the lighting duty cycle of the WB-AC LED II is 60%. From Fig. 6, it is found that the WPE of the WB-AC LED II is 4.3% and the averaged input power is 0.64 W under AC 110 V operated, but the WPE of the WB-AC LED II with the identical input power under DC operated is 5.3%. It is speculated that the fluctuant output power caused by the AC source will decrease the efficiency of WB-AC LED.