Efficient Quantum-Dot Light-Emitting Diodes Enabled via a Charge Manipulating Structure.

Charge carriers are the basic physical element in an electrically driven quantum-dot light-emitting diode (QLED), which acts as a converter transforming electric energy to light energy. Therefore, it is widely sought after to manage the charge carriers for achieving efficient energy conversion; however, to date, there has been a lack of understanding and efficient strategies. Here, an efficient QLED is achieved by manipulating the charge distribution and dynamics with an n-type 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi) layer embedded into the hole-transport layer. Compared with the control QLED, the maximum current efficiency of the TPBi-containing device is enhanced over 30%, reaching 25.0 cd/A, corresponding to a 100% internal quantum efficiency considering the ∼90% photoluminescence quantum yield of the QD film. Our results suggest that there is still a great deal of room to further improve the efficiency in a standard QLED by subtly manipulating the charge carriers.