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Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
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A generalized Stark effect electromodulation model for extracting excitonic properties in organic semiconductors
Taili Liu1,2,3, Yishu Foo1,2, Juan Antonio Zapien1,2
1Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Ave, Kowloon Tong, Hong Kong SAR, P. R. China.
Nature Communications
|November 10, 2019
Summary
Electromodulation (EM) spectroscopy accurately determines material properties by accounting for optical interference and electrorefraction. This new model ensures consistent results across different device geometries, improving excitonic property analysis.
Area of Science:
- Materials Science
- Spectroscopy
- Optoelectronics
Background:
- Electromodulation (EM) spectroscopy is vital for studying excitonic properties by measuring changes in polarizability and dipole moment.
- Extracting these changes (Δp and Δu) traditionally relies on optical absorption fitting, which can vary significantly with device geometry.
Purpose of the Study:
- To systematically investigate electromodulation spectroscopy in reflection and transmission modes.
- To identify and address the causes of discrepancies in extracted Δp and Δu values.
- To develop a generalized model for accurate excitonic property determination.
Main Methods:
- Conducted a systematic electromodulation study using various fitting approaches.
- Employed both reflection and transmission device architectures.
- Developed and applied a generalized electromodulation model incorporating optical interference and electrorefraction.
Main Results:
- Deviations previously attributed to continuum states were found to stem from overlooked optical interference and electrorefraction effects.
- The generalized model successfully incorporated these effects.
- Extracted Δp and Δu values showed excellent consistency across reflection and transmission modes for all organic film thicknesses.
Conclusions:
- The generalized electromodulation model provides a more accurate method for extracting material properties.
- This approach resolves inconsistencies observed in previous studies, particularly concerning continuum state thresholds.
- The findings enhance the reliability of EM spectroscopy for analyzing excitonic properties in various device configurations.
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