Crosslinked conjugated polymers as hole transport layers in high-performance quantum dot light-emitting diodes

Area of Science:

• Materials Science
• Organic Electronics
• Photochemistry

Background:

• Film morphology in solution-processed quantum dot light-emitting diodes (QLEDs) is critical for device efficiency.
• Orthogonality of solvents for adjacent layers is typically required to prevent layer dissolution.

Purpose of the Study:

• To develop a method for creating solvent-resistant hole transport layers (HTLs).
• To improve the performance of all-solution-processed QLEDs by controlling film morphology.
• To enable the use of non-orthogonal solvents in multilayer device fabrication.

Main Methods:

• Photochemical crosslinking of HTLs using bifunctional bis-benzophenone (BP-BP) photoinitiator.
• Fabrication of ultra-smooth quantum dot (QD) layers using toluene on crosslinked HTLs.
• Device performance characterization of green QLEDs with crosslinked and non-crosslinked HTLs.

Main Results:

• Crosslinked HTLs demonstrated excellent solvent resistance, enabling QD layer deposition with toluene.
• Green QLEDs with crosslinked HTLs achieved a 1.9-fold higher external quantum efficiency (8.93%) compared to non-crosslinked devices.
• The crosslinking strategy prevented intermixing between QD and HTL layers, preserving film morphology.

Conclusions:

• Photochemical crosslinking of HTLs is an effective strategy to enhance QLED performance and enable the use of non-orthogonal solvents.
• This method avoids high-temperature annealing, facilitating the fabrication of flexible QLEDs on plastic substrates.
• The approach broadens solvent choices for solution-processed multilayer optoelectronic devices.