High-resolution photoluminescence electro-modulation microscopy by scanning lock-in

Area of Science:

• Organic electronics
• Semiconductor physics
• Advanced microscopy techniques

Background:

• Morphological inhomogeneities and defects in organic semiconductors significantly impact charge transport.
• Organic thin-film transistors (OTFTs) performance is directly linked to charge accumulation and lateral transport.
• Photoluminescence Electro-Modulation (PLEM) microscopy visualizes charge distribution by detecting fluorescence modulation.

Purpose of the Study:

• To develop an enhanced PLEM microscopy technique with improved resolution and contrast.
• To investigate the spatial distribution of charge carriers in organic semiconductors.
• To demonstrate the capability of the enhanced PLEM for analyzing charge accumulation variations.

Main Methods:

• Implemented a lock-in detection scheme synchronized with a scanning laser beam.
• Modulated charge density sinusoidally and phase-locked it to the excitation laser scan.
• Acquired multiple images at different phase shifts between beam scan and electrical modulation.

Main Results:

• Achieved sub-300 nm diffraction-limited resolution.
• Obtained a signal-to-noise ratio of 21.4 dB.
• Successfully imaged local variations in charge accumulation in an organic transistor.

Conclusions:

• The enhanced PLEM microscopy offers superior resolution and contrast for charge imaging in organic semiconductors.
• This technique is valuable for understanding charge carrier behavior and device performance.
• High-resolution PLEM provides insights into local inhomogeneities affecting charge accumulation.