Recent progress in hole-transporting materials and inkjet-printing QLEDs

Quantum dot light-emitting diodes (QLEDs) have attracted a great deal of interests due to their unique advantages such as tunable spectrum, high color saturation, compatibility with low-cost inkjet-printing (IJP) technology and potential for use in large-area full-color pixelated display. To date, the efficiency and lifetime of red, green, and blue QLEDs have been significantly improved, in which hole-transporting materials (HTMs) play the key role in determining the device performance. In this review, we highlight to summarize the diverse types of HTMs in QLEDs, including small-organic materials, polymers, crosslinkable materials and inorganic p-type semiconductors, and their properties such as charge carrier mobility, thermal stability, and structural configuration are also reviewed. The significant effects of these properties on device performances are discussed, which would help to understand device physics and improve their performances and reliability of QLEDs. In addition, the development of IJP for QLEDs fabrication and the influence factors of IJP on quantum dot film-forming property are also reviewed, in an effort to provide guidance to continue the advancement of QLED displays.