On the Electroluminescence Turn-On Mechanism of Blue Quantum-Dot Light-Emitting Diodes

摘要

A clear understanding on the fundamental working mechanisms of quantumdotlight emitting diodes (QLEDs), especially the blue devices, is alwayssought after. Here the electroluminescence (EL) turn-on mechanism of blueQLEDs is unraveled by structure engineering of the hole-transport layers(HTLs). It is demonstrated that the EL turn-on in blue QLEDs is highlydependent on the charge-transport polarity of the HTLs. Energy transferbetween HTLs and the blue quantum dots (QDs) occurs for the QLEDsbased on bipolar HTLs, and, in contrast, charge injection is responsible forEL turn-on of the blue devices consisting of unipolar HTLs. In addition, largehole-injection barrier results in serious accumulation of holes at the interfaceof HTLs/QDs, then inducing serious electrons leakage into the HTLs, therebyleading to poor device efficiency under low driving current. It is suggestedhere that confining the carriers to the quantum dots and reducing the holeinjectionbarrier remain two critical aspects to optimize the performance ofblue QLEDs.