A Novel Crosslinked Hole Transport Layer with Enhanced Charge Injection Balance for Highly Efficient Inkjet-Printed
Liming Xie1,2, Jinrong Shi2, Ting Wang2
1Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, China.
ACS Applied Materials & Interfaces
|September 4, 2024
Summary
A novel blended hole transport layer (HTL) enhances blue quantum dot light-emitting diodes (QLEDs). This crosslinked HTL improves charge balance, stability, and efficiency for both spin-coated and inkjet-printed QLEDs.
Area of Science:
- Materials Science
- Organic Electronics
- Optoelectronics
Background:
- High-performance and stable blue quantum dot-based light-emitting diodes (QLEDs) are crucial for next-generation displays and lighting.
- Developing efficient hole transport layers (HTLs) is essential for optimizing charge injection, balance, and device stability in QLEDs.
Purpose of the Study:
- To introduce an efficient and robust blended hole transport layer (HTL) for high-performance and stable blue QLEDs.
- To investigate the properties of a blended HTL comprising poly((9,9-dioctylfluorenyl-2,7-diyl)-alt-(9-(2-ethylhexyl)-carbazole-3,6-diyl)) (PF8Cz) and crosslinkable 3,3'-(9,9-dimethyl-9H-fluorene-2,7-diyl)bis(9-(4-vinylphenyl)-9H-carbazole) (FLCZ-V).
Main Methods:
- Synthesized and blended PF8Cz and FLCZ-V to form the HTL.
- Investigated the in situ crosslinking behavior of FLCZ-V upon thermal treatment.
- Characterized the morphological, electrical, and surface properties of the blended HTL.
- Fabricated blue QLEDs using both spin-coating and inkjet printing techniques with the developed HTL.
Main Results:
- The blended HTL exhibited high hole mobility (1.27 × 10⁻⁴ cm²/V·s) and gradient HOMO levels facilitating hole injection.
- The crosslinked HTL demonstrated excellent solvent resistance and high surface energy (40.34 mN/m), improving wettability and interfacial contact.
- Spin-coated blue QLEDs achieved a remarkable external quantum efficiency (EQE) of 15.5%.
- Inkjet-printed blue QLEDs reached an EQE of 9.2%, representing a state-of-the-art performance for this fabrication method.
Conclusions:
- The developed blended HTL significantly enhances the performance and stability of blue QLEDs.
- The in situ crosslinking strategy provides a robust and efficient HTL suitable for various fabrication methods, including inkjet printing.
- This work offers a promising pathway for realizing high-efficiency, solution-processed blue QLEDs.
