High-efficiency inverted quantum dot light-emitting diodes with enhanced hole injection.

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Colloidal quantum dot light-emitting diodes (QLEDs) are promising display technologies.
• Efficient charge injection is crucial for optimizing QLED performance.
• Hybrid organic-inorganic interlayers offer potential for enhanced device characteristics.

Purpose of the Study:

• To investigate the efficacy of hybrid molybdenum trioxide (MoO3)/1,4,5,8-naphthalenetetracarbonitrile (HAT-CN) as a hole injection layer (HIL) in green inverted QLEDs.
• To evaluate the impact of the hybrid HIL on electroluminescent properties and device efficiency.
• To understand the charge transport mechanisms influenced by the hybrid HIL.

Main Methods:

• Fabrication of green inverted QLEDs utilizing hybrid MoO3/HAT-CN as the HIL.
• Characterization of device performance, including turn-on voltage, current efficiency, and external quantum efficiency.
• Electrical analysis of hole-only devices to assess hole injection and leakage current.

Main Results:

• The optimal hybrid HIL (1.5 nm MoO3/2.5 nm HAT-CN) resulted in a turn-on voltage of 1.9 V, a maximum current efficiency of 41.3 cd A-1, and a maximum external quantum efficiency of 9.72%.
• Hybrid HILs improved the maximum current efficiency of hole-only devices by 1.6 and 1.5 times compared to single MoO3 or HAT-CN interlayers, respectively.
• Hybrid HILs demonstrated reduced leakage current at low voltages and significantly enhanced hole injection compared to single interlayers.

Conclusions:

• Hybrid MoO3/HAT-CN HILs effectively enhance hole injection efficiency and suppress space charge accumulation in green inverted QLEDs.
• The improved charge carrier balance leads to significantly enhanced electroluminescent efficiency.
• The hybrid HIL approach is extendable to other color inverted QLEDs for display applications, promising bright, efficient, and color-saturated devices.