Mixed-Polymer Hole Transport Layers Reinforce Au-Anode Top Emitting Perovskite Light Emitting Diodes

Area of Science:

• Materials Science
• Optoelectronics
• Chemistry

Background:

• Metal halide perovskite light-emitting diodes (PeLEDs) show promise but suffer from limited operational stability.
• Degradation often stems from byproducts of interfacial electrochemistry reacting with device layers, especially metal anodes.
• Corrosion of metal anodes leads to increased leakage current and decreased emission intensity in PeLEDs.

Purpose of the Study:

• To enhance the operational stability of methylammonium lead iodide-based PeLEDs with gold (Au) metal anodes.
• To investigate the use of a mixed-polymer hole transport layer (HTL) to mitigate anode degradation.
• To understand the mechanism by which the mixed-polymer HTL improves PeLED stability.

Main Methods:

• Fabrication of PeLEDs utilizing a mixed-polymer HTL composed of poly(N,N'-bis-4-butylphenyl-N,N'-bisphenyl)benzidine (polyTPD) and poly(9-vinylcarbazole) (PVK).
• Testing device performance under repeated operation and constant driving to assess stability against leakage current and emission decay.
• Employing a newly developed Au-corrosion-based triiodide detection experiment to analyze interfacial chemistry.

Main Results:

• The mixed-polymer HTL effectively stabilized the PeLEDs, reducing leakage current and emission intensity decrease during operation.
• The stabilization was attributed to the mixed HTL's ability to interfere with and inhibit triiodide transport.
• This inhibition of triiodide transport prevented the corrosion and degradation of the gold metal anode.

Conclusions:

• A mixed-polymer HTL comprising polyTPD and PVK offers a viable strategy for enhancing the stability of perovskite LEDs.
• The study demonstrates a new method for detecting triiodide and understanding its role in device degradation.
• This approach leads to more robust and longer-lasting PeLED devices by protecting critical metal anode components.