Solution‐Processable Small‐Molecule Hole Transport Material for High‐Performance QLED via Manipulating Dipole Moments

Abstract Solution‐processed quantum‐dot light‐emitting diodes (QLEDs) have achieved huge successes in terms of both efficiency and stability. However, the polymeric hole transport materials (HTMs) utilized in QLEDs, to some degree, cause severe damages to performance consistency due to their intrinsic batch‐to‐batch problems. Thus, adopting small‐molecule HTMs with definitive chemical structures and molecular weight is a plausible way to solve this issue. In this work, a new solution‐processable small‐molecule (SM)‐HTM (FLCZ) is designed and synthesized, through elaborately modifying the widely used 4,4′‐bis(carbazole‐9‐yl)‐biphenyl via manipulating dipole moments, for solution‐processed QLEDs to replace polymeric HTMs. The FLCZ‐based QLED has achieved an external quantum efficiency (EQE) of 14.63% (18.74 lm W −1 , 20.01 cd A −1 ), approaching that of polymer HTMs‐based QLEDs. In addition, the large surface energy of 45.29 mN m −1 is also observed on the film of FLCZ, which is highly desirable for inkjet‐printed (IJP) QLED devices, results in the IJP fabricated QLED with an EQE of 10.69%. To the best of knowledge, the results of this work represent the highest device performance of conventional solution‐processed QLED based on a single SM‐HTM.