Multimodal electron microscopy of halide perovskite interfacial dynamics

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Halide perovskite light-emitting diodes (PeLEDs) offer high efficiency and low cost but suffer from operational instability.
• This instability is a major obstacle for their widespread commercial application.

Purpose of the Study:

• To investigate the nanoscale degradation mechanisms in working PeLEDs.
• To establish a link between interfacial phenomena and device instability.

Main Methods:

• Developed a multimodal in situ electron microscopy technique.
• Integrated 4D scanning transmission electron microscopy (4D-STEM), energy-dispersive X-ray spectroscopy (EDX), and atomic-resolution imaging.
• Performed in situ biasing measurements on working PeLEDs.

Main Results:

• Observed nanoscale structural and chemical evolution at transport layer interfaces.
• Identified formation of metallic lead and lead-rich secondary phases.
• Documented strain-driven grain fragmentation and transformation of the aluminum contact to aluminum chloride (AlCl3).
• Degradation was localized at interfaces, with the perovskite bulk remaining largely intact.

Conclusions:

• Established a mechanistic link between interfacial strain, ionic transport, and electrochemical reactions.
• Provided a framework for nanoscale degradation analysis in complex optoelectronic systems.
• Highlighted the critical role of interfaces in PeLED operational instability.