Ultrahighly Efficient White Quantum Dot Light‐Emitting Diodes Operating at Low Voltage

Achieving efficient white quantum dot light‐emitting diodes (WQLEDs) is highly desired because of their promising applications in general illumination and display backlight systems. Herein, a highly efficient WQLED with an extremely low input voltage is reported, which is fabricated via an all‐solution process by using an emitting layer with a mixture of red‐, blue‐, and green‐emitting quantum dots. When a facile strategy of light outcoupling with an optical lens is introduced, the device shows a maximum external quantum efficiency of 28.4%, which is the highest value reported so far. Moreover, the device exhibits a standard white emission with International Commission on Illumination (CIE) coordinates of (0.36, 0.34) at an extremely low input voltage of 3.2 V. This work provides a promising way for achieving high‐performance white quantum‐dot light‐emitting diodes with low driving voltage. An efficient white quantum‐dot light‐emitting diode with a maximum external quantum efficiency of 28.4% and a peak luminance of 74 363 cd m−2 is obtained. Moreover, by light outcoupling a pure white emission with International Commission on Illumination (CIE) coordinates of (0.33, 0.34) can be achieved at an extremely low voltage of 3.4 V.