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High Current Injection into Dynamic p-n Homojunction in Polymer Light-Emitting Electrochemical Cells.
Tomo Sakanoue1, Jinpeng Li2, Hisaaki Tanaka1
1Department of Applied Physics, Nagoya University, Chikusa, Nagoya, 464-8603, Japan.
Advanced Materials (Deerfield Beach, Fla.)
|March 7, 2017
Summary
Researchers improved light-emitting electrochemical cells (LECs) by controlling ion and electron charges separately. This breakthrough enhances polymer brightness and device speed, overcoming previous stability and response limitations.
Area of Science:
- Materials Science
- Electrochemistry
- Polymer Science
Background:
- Polymer-electrolyte blends enable light-emitting electrochemical cells (LECs) via in situ p-n homojunctions for charge transport.
- LECs suffer from stability and speed issues due to limited electrochemical stability and low ion mobility, causing dimness and slow responses.
Purpose of the Study:
- To overcome the stability and speed limitations of LECs.
- To enhance charge injection and transport efficiency in polymer-based devices.
- To achieve brighter and faster polymer light-emitting electrochemical cells.
Main Methods:
- Implemented a driving pulse technique with a base voltage to separately control ionic and electronic charges.
- Applied a constant base voltage for ion rearrangement and a superimposed high-voltage pulse for fast electron/hole injection.
- Utilized in situ electron spin resonance (ESR) measurements to analyze polymer doping and structure.
Main Results:
- Achieved extremely high current density (> 2 kA cm-2) with a balanced electron/hole ratio.
- Demonstrated a high-speed response time of approximately 50 ns.
- Observed highly doped polymers with spin density up to 7 × 1019 spins cm-3 and an ordered polymer structure.
Conclusions:
- The separate control of ionic and electronic charges significantly enhances LEC performance.
- High doping levels and ordered polymer structure are crucial for the improved brightness and speed.
- This method offers a promising pathway for brighter and faster polymer-based light-emitting devices.
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