Dynamic doping in bright and stable light emitting electrochemical cells

Area of Science:

• Organic electronics
• Solid-state devices
• Optoelectronics

Background:

• Light-emitting electrochemical cells (LECs) offer promising optoelectronic properties.
• Understanding their operational dynamics under voltage driving is crucial for performance optimization.
• Ion migration significantly influences LEC device physics and stability.

Purpose of the Study:

• To investigate the device operation of sandwiched LECs under normal voltage driving.
• To elucidate the mechanisms behind conductivity changes and their impact on device performance.
• To explore methods for controlling dynamic doping and improving LEC characteristics.

Main Methods:

• Utilized fast current density and luminance versus voltage (JL-V) analysis.
• Performed JL-V scans under specific conditions to ensure meaningful data acquisition.
• Analyzed space-charge limited current behavior and conductivity changes.

Main Results:

• Observed space-charge limited current behavior after overcoming injection barriers.
• Identified reduced effective device thickness due to the formation of conductive regions near electrodes.
• Demonstrated that ion compensation of injected electrons enhances carrier concentration, akin to electrochemical doping.

Conclusions:

• Fast JL-V analysis is essential for meaningful studies of LEC operation.
• Conductivity enhancement in LECs results from ion-assisted carrier concentration increase.
• Pulsed current driving schemes can control dynamic doping, leading to sub-second turn-on and long device lifetimes.