Stable Quantum Dot Light‐Emitting Diodes Compatible With Household Alternating Current Electricity

Abstract

ABSTRACT Like other p‐n junction devices, quantum dot light‐emitting diodes (QLEDs) can only operate with direct current (DC), which is incompatible with household 220 V/50 Hz alternating current (AC), and accelerates device degradation due to constant charge injection and accumulation. Here, we develop a tandem QLED consisting of two QLEDs with opposite polarity that are connected in parallel. These QLEDs turn on alternately during positive and negative AC half‐cycles, enabling them to operate directly under AC while maintaining high efficiency. More importantly, accumulated charges are effectively extracted under AC driving, and the T 95 lifetime at 10,000 cd m − 2 extends from 95 to 279 h. However, when powered by AC electricity, the tandem QLEDs exhibit an undesirable luminance flicker that is caused by the dark intervals occurring when the sinusoidal AC voltage is lower than the QLEDs' turn‐on voltage. To address this issue, we develop a multi‐phase driving scheme that uses phase‐shifted AC signals to compensate for the dark intervals, and as a result, the percentage of flicker is effectively reduced from 100% to 13%. The developed device architecture and driving scheme result in high‐efficiency, long‐lifetime, low‐flicker QLEDs that can be used as plug‐and‐play lighting sources compatible with household AC electricity.