A hole transport material with low cross-linking temperature for high-performance blue quantum dot light-emitting diodes

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Abstract
Inefficient hole injection poses a major challenge in the realization of stable and economically feasible solution-processed blue quantum dot light-emitting diodes (QLEDs). The advancement of hole transport materials (HTMs) for the realization of high-performance blue QLEDs has demonstrated considerable challenges, primarily attributed to their intrinsic low hole mobility and mismatched energy levels. Herein, two vinyl-based cross-linkable HTMs, 4,4′-bis(3-vinyl-9H-carbazol-9-yl)-1,1′biphenyl (CBP-V) and 2,8-bis(3-vinyl-9H-carbazol-9-yl)dibenzo[b,d]thiophene (KSP-V), are designed and synthesized. Compared with CBP-V, KSP-V possesses a relatively low cross-linking temperature of 190 °C with a nearly 100% solvent resistance. Moreover, KSP-V exhibits exceptional hole transport properties, with a notable 4.2-fold enhancement in hole mobility. By substituting thiophene groups for biphenyl groups, the highest occupied molecular orbital level of KSP is reduced to −5.92 eV. When applying KSP to solution-processed blue QLEDs [Commission Internationale de l'Eclairage coordinates of (0.15, 0.03)], the devices exhibit excellent properties. Particularly, the maximum luminance of 27 036 cd m−2 and external quantum efficiency of 15.69%. Our work provides important guidance for the rational design of cross-linkable HTMs for solution-processed blue QLEDs.
Funding Information
  • Finded by Science Research Project of Hebei Education Department (QN2025180)
  • Hebei Minzu Normal University Fund Project (DR2024015)
  • Natural Science Foundation of Shandong Province (No. ZR2024QB372)
  • National Natural Science Foundation of China (No. 52203260)
  • Hundred Outstanding Talent Program of Jining Unversity (No. 2023ZYRC39)
  • Natural Science Foundation of Shandong Province (ZR2024ME167)

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