Balanced carrier injection of quantum dots light-emitting diodes: the case of interface barrier of bilayer ZnO electron transport layer

Unbalanced carrier injection is one of the most important reasons for the efficiency roll-off in quantum dot light-emitting diodes. Reducing the electron injection can effectively balance the carrier transport and improve the optoelectronic performance of the device. In this work, a bilayer ZnO electron transport layer was fabricated by twice spin-coating and annealing methods. More than 60% of electrons are effectively blocked by the ZnO interface barrier compared with the standard device, resulting in increasing the maximum luminance of the device from 25 390 to 48 220 cd m(-2) and the current efficiency from 1.5 to 3.2 cd A(-1).