White light-emitting electrochemical cells based on metal-free TADF emitters

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• White light-emitting electrochemical cells (LECs) are crucial for cost-efficient and sustainable lighting applications.
• Current white LECs often rely on non-sustainable metals or are limited by inefficient singlet exciton conversion.
• Thermally activated delayed fluorescence (TADF) organic compounds offer a metal-free alternative capable of harvesting all excitons.

Purpose of the Study:

• To report the development of the first white LEC utilizing solely metal-free TADF emitters.
• To demonstrate efficient white light emission by optimizing energy transfer and doping structures in a single-layer active material.

Main Methods:

• Design and synthesis of metal-free TADF emitters.
• Fabrication of a single-layer LEC device.
• Careful tuning of energy-transfer processes and electrochemical doping within the active layer.

Main Results:

• Successful fabrication of a white LEC based exclusively on metal-free TADF emitters.
• Achieved angle-invariant white light emission with a high color rendering index (CRI) of 88.
• Demonstrated an external quantum efficiency of 2.1% at a luminance of 350 cd/m².

Conclusions:

• This work presents a significant advancement in sustainable lighting by introducing the first metal-free TADF-based white LEC.
• The developed technology overcomes the limitations of existing white LECs, offering a potentially more efficient and environmentally friendly solution.
• The findings pave the way for future development of high-performance, sustainable organic lighting devices.