Balancing multiple properties of small molecule hole-transporting materials towards highly efficient perovskite QLEDs

Abstract

Organic hole-transporting materials (HTMs) play critical roles in the performances and stability of perovskite quantum dot light-emitting diodes (Pe-QLEDs). Ideal HTMs for Pe-QLEDs must satisfy three key principles: high hole mobility, energy level alignment, and interface passivation. However, the combined effects of these factors on Pe-QLED performances have not been thoroughly understood. In this study, we tailor-made three carbazole-based dendritic small-molecule HTMs, named X51, X52, and X53, each with distinct optical and physical properties for application in Pe-QLEDs. Our findings revealed that X51 exhibited a highest hole mobility but had a high energy barrier, while X53 demonstrated the best interface passivation effect but suffered from the lowest hole mobility. In contrast, the X52 achieved the best balance of properties, resulting in Pe-QLEDs with the highest external quantum efficiency (EQE) of 23.78% (the highest reported for small molecule HTM-based Pe-QLEDs to date), significantly outperforming devices based on X51 (5.52%) and X53 (12.73%). This outcome, akin to the “bucket effect”, underscores the importance of balancing multiple properties in the design of small-molecule HTMs. These results not only present a high-performance small-molecule HTM but also provide crucial insights for comprehensively considering multiple design factors in the HTM development. © 2024 Elsevier B.V.