Promoted Hole Transport Capability by Improving Lateral Current Spreading for High-Efficiency Quantum Dot...

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Carrier imbalance, particularly stronger electron injection than hole injection, limits quantum-dot light-emitting diode (QLED) performance.
• Molybdenum trioxide (MoO3) and (4,4'-bis(N-carbazolyl)-1,1'-biphenyl) (CBP) are materials relevant to charge transport layers.

Purpose of the Study:

• To enhance the performance of inverted QLEDs by addressing carrier imbalance.
• To investigate the effect of periodically inserting ultrathin MoO3 into the CBP hole transport layer (HTL).

Main Methods:

• Fabrication of inverted QLEDs with periodic MoO3/CBP stacked HTLs.
• Characterization of photoelectric properties and device performance.
• Optimization of MoO3 interlayer thickness.

Main Results:

• Periodic insertion of ultrathin MoO3 into CBP HTL improved lateral current spreading and hole transport.
• Optimal MoO3 interlayer thickness was found to be approximately 1 nm.
• Devices with two MoO3 insertions achieved a peak current efficiency of 88.7 cd A-1 and an external quantum efficiency of 20.6%.

Conclusions:

• The MoO3/CBP HTL effectively mitigates carrier imbalance in QLEDs.
• The optimized QLEDs demonstrate significantly improved efficiency and a 2.5x longer operational lifetime compared to CBP-only devices.
• This approach offers a viable strategy for developing high-performance QLEDs.