Diffusion-mediated resonant energy transfer in lanthanide-based polymer white-light-emitting diodes

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Development of efficient white light-emitting diodes (WOLEDs) is crucial for next-generation lighting and display technologies.
• Organic light-emitting diodes (OLEDs) offer advantages like flexibility and low-cost fabrication, but achieving pure white emission with high efficiency remains a challenge.
• Lanthanide complexes are explored for their unique photoluminescent properties, potentially enabling novel emissive materials.

Purpose of the Study:

• To present a novel single-layer, polymer WOLED based on organic lanthanide complexes.
• To investigate the mechanisms responsible for white light emission in the developed device.
• To quantitatively evaluate the energy transfer processes and determine key photophysical parameters.

Main Methods:

• Fabrication of a single-layer polymer WOLED using solution processing techniques.
• Characterization of the device's electroluminescence properties, including CIE coordinates.
• Analysis of electroluminescence mechanisms, focusing on charge trapping and energy transfer.
• Quantitative evaluation of excitation diffusion and determination of singlet exciton diffusion coefficients and lengths.

Main Results:

• The fabricated WOLED exhibits high color purity white light emission with CIE coordinates of (0.33, 0.38).
• Electroluminescence originates from both direct charge trapping on lanthanide complexes and efficient diffusion-assisted energy transfer from the host matrix.
• An expression for steady-state transfer efficiency was derived and validated.
• Singlet exciton diffusion coefficients and diffusion lengths in the host material were quantitatively determined.

Conclusions:

• The study successfully demonstrates a solution-processed polymer WOLED with high color purity white light using novel organic lanthanide complexes.
• The findings elucidate the synergistic roles of charge trapping and long-range energy transfer in achieving efficient white light emission.
• The quantitative evaluation of excitation diffusion provides valuable insights for designing and optimizing future organic light-emitting devices.