Stable, Efficient Near-Infrared Light-Emitting Diodes Enabled by α/δ Phase Modulation

Area of Science:

• Optoelectronics
• Materials Science
• Solid-State Chemistry

Background:

• Formamidinium lead iodide (FAPbI3) is a promising optoelectronic material.
• Its application is hindered by phase instability, converting from the desired black (α) to yellow (δ) phase.
• Developing stable FAPbI3-based devices requires addressing this phase transition.

Purpose of the Study:

• To enhance the stability and efficiency of FAPbI3 perovskite for near-infrared light-emitting diodes (NIR PeLEDs).
• To investigate the effect of diamine cations, specifically 2,2-(ethylenedioxy)bis(ethylamine) (EDBE), on FAPbI3 phase stability and device performance.
• To understand the mechanism by which EDBE influences the α/δ phase transition and improves device longevity.

Main Methods:

• Introduction of diamine cations (EDBE) into the FAPbI3 perovskite structure.
• Fabrication of NIR PeLEDs utilizing the modified FAPbI3 material.
• Characterization of the perovskite film's phase stability, optical properties, and device performance, including external quantum efficiency (EQE).
• Assessment of device stability under ambient conditions over an extended period (270 days).

Main Results:

• Successful preparation of NIR PeLEDs with an external quantum efficiency (EQE) up to 11.40%.
• Demonstrated excellent stability of the EDBE-modified perovskite film, showing no significant degradation after 270 days in air.
• Evidence that EDBE introduction reduces the formation energy of the α-FAPbI3 phase.
• Observed increased stability attributed to hydrogen bonds formed between adjacent EDBE molecules.

Conclusions:

• The incorporation of EDBE cations effectively stabilizes the α-FAPbI3 phase, crucial for optoelectronic applications.
• EDBE-modified FAPbI3 enables the development of stable and efficient NIR PeLEDs.
• This study provides insights into the phase transition mechanisms of FAPbI3 and offers a strategy for improving perovskite-based LED performance and longevity.