Efficient deep-blue electroluminescence from Ce-based metal halide

Area of Science:

• Materials Science
• Solid-State Physics
• Optoelectronics

Background:

• Rare earth ions (Ce³⁺, Eu²⁺) are promising for electroluminescence due to their spectral properties, efficiency, and stability.
• Direct charge injection into 4f orbitals is challenging, limiting external quantum efficiency and increasing operating voltage in rare earth light-emitting diodes (LEDs).

Purpose of the Study:

• To propose and investigate an energy transfer scheme to overcome limitations in rare earth ion-based LEDs.
• To enhance the performance of cerium-based LEDs by optimizing energy transfer pathways.

Main Methods:

• Utilized X-ray photoelectron spectroscopy (XPS) to analyze material composition and electronic states.
• Employed transient absorption spectroscopy to study excited-state dynamics and energy transfer processes.
• Fabricated and characterized light-emitting diodes incorporating Cs₃CeI₆ as the active layer.

Main Results:

• Demonstrated that the luminescence in Cs₃CeI₆ is primarily driven by energy transfer from I₂-based self-trapped excitons to Ce-based Frenkel excitons.
• Showed that enhancing spectral overlap between self-trapped exciton emission and Ce-based Frenkel exciton excitation significantly improves energy transfer efficiency.
• Achieved a maximum brightness of 1073 cd/m² and an external quantum efficiency of 7.9% in the fabricated LEDs.

Conclusions:

• The proposed energy transfer strategy effectively addresses the challenge of direct charge injection into 4f orbitals.
• Optimized spectral overlap is crucial for efficient energy transfer in rare earth-based luminescence systems.
• The developed Cs₃CeI₆ LEDs exhibit promising performance for electroluminescence applications.