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Nanoscale conjugated-polymer light-emitting diodes.
Farhad A Boroumand1, Paul W Fry, David G Lidzey
1Department of Physics and Astronomy, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, UK.
Nano Letters
|March 29, 2005
Summary
We patterned indium tin oxide (ITO) electrodes for conjugated-polymer LEDs with 100 nm contacts. Current spreading in the PEDOT:PSS layer caused electroluminescence broadening to approximately 170 nm.
Area of Science:
- Materials Science
- Electrical Engineering
- Optoelectronics
Background:
- Conjugated-polymer LEDs (CPLEDs) are promising for flexible electronics.
- Precise control over device dimensions is crucial for performance.
- Hole injection layers can influence charge transport and emission characteristics.
Purpose of the Study:
- To investigate the effect of small electrode dimensions on CPLED electroluminescence.
- To analyze current spreading phenomena in CPLEDs with patterned ITO electrodes.
- To understand the role of the PEDOT:PSS layer in charge transport.
Main Methods:
- E-beam lithography was employed to pattern indium tin oxide (ITO) electrodes.
- Arrays of conjugated-polymer LEDs with 100 nm diameter hole-injecting contacts were fabricated.
- Optical microscopy was used to estimate the electroluminescence region diameter.
Main Results:
- Electroluminescence from 100 nm diameter LEDs originated from a region of approximately 170 nm diameter.
- A significant broadening of the emission zone was observed compared to the electrode size.
- Current spreading within the PEDOT:PSS layer was identified as the cause for this broadening.
Conclusions:
- The effective emission area in small-scale CPLEDs is larger than the physical electrode size due to current spreading.
- PEDOT:PSS layer significantly impacts charge distribution and emission characteristics in CPLEDs.
- Understanding current spreading is essential for optimizing the design and performance of nanoscale CPLEDs.