Balanced charge injection promises high efficiency of quantum dot-based light-emitting diodes (QD-LEDs). The most widely used approach to realize charge injection balance impedes the injection rate of the dominant charge carrier with energetic barriers. However, these approaches often accompany unwanted outcomes (e.g., the increase in operation voltage) that sacrifice the operational stability of devices. Herein, a "positive incentive" approach is proposed to enhance the efficiency and the operational stability of QD-LEDs. Specifically, the supply of hole, an inferior carrier than its counterpart, is facilitated by adopting a thin fullerene (C60) interlayer at the interface between the hole injection layer (MoOX) and hole transport layer (4,4'-bis(9-carbazolyl)-1,1'-biphenyl). The C60 interlayer boosts the hole current by eliminating the universal energy barrier, lowers the operation voltage of QD-LEDs, and enhances the charge balance in the QD emissive layer within the working device. Consequently, QD-LEDs benefitting from the adoption of the C60 interlayer exhibit significantly enhanced device efficiency and operation stability. Grounded on the quantitative assessment of the charge injection imbalance within the QD emissive layer, the impact of electrical parameters of QD-LEDs on their optoelectronic performance and operational stability is also discussed.
Keywords: charge injection balance; fullerene; hole injection barrier; operational stability; quantum dot-based light-emitting diodes.