A record-breaking low turn-on voltage blue QLED via reducing built-in potential

Developing light-emitting diodes (LEDs) with the merits of low driving and high brightness has always been attractive. Considering the carrier dynamic process under electroexcitation, the built-in potential (Vbi) represents the moment that the photons start to be produced in a LED. However, it has not been carefully studied and discussed. Here, we observed that by employing an interface regulation strategy to enhance hole concentration, the Vbi of quantum dot LEDs (QLEDs) can be reduced. Combined with the characterization methods of Mott–Schottky (MS) and scanning Kelvin probe microscopy (SKPM), the key indicator of Vbi on driving voltage for QLEDs is confirmed. Profiting from the reduction of Vbi, a record-breaking ultra-low turn-on voltage of 2.2 V (@1 cd/m2) is achieved in a blue QLED. The blue QLED shows an advantage of high brightness under low driving voltages, i.e., 1000 cd/m2@3.10 V and 5000 cd/m2@3.88 V. This work proposes a reference strategy to predict and analyze the driving voltage issue, which is beneficial to facilitating the development of low-driving QLEDs in the future.