Micrometer-scale-thick quantum-dot LEDs with notably enhanced stability and ultrahigh brightness

The thickness of quantum-dot light-emitting diodes (QLEDs) is typically limited to around 100 nm, which could lead to the formation of short-circuit paths that ultimately reduce the device performance. Here, we develop micrometer-scale-thick QLEDs by using extremely conductive ZnMgO as an electron transport layer. With a H2O-regulated doping method, the electron concentration of the ZnMgO film is greatly increased, which results not only in the ohmic injection but also in the trap-free electron transport. As a result, micrometer-scale-thick QLEDs, with thickness of more than 10 times that of standard QLEDs, are achieved. The demonstrated micrometer-thick red QLEDs not only can be directly built on various substrates such as Cu slabs, Ag nanowire-coated substrate, Al foils, and printing papers but also can exhibit a notably enhanced T90 life span over 11,000 hours at 1000 candelas per square meter and an ultrahigh brightness of 3,941,000 candelas per square meter, which represent 5.03- and 4.36-fold improvements over those of conventional QLEDs.