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Spectrally Resolved Exciton Polarizability for Understanding Charge Generation in Organic Bulk Hetero-Junction Diodes
Enoch Go1,2, Hyunjung Jin1,2, Seongwon Yoon1
1Advanced Photovoltaics Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea.
Journal of the American Chemical Society
|May 17, 2024
Summary
Understanding charge generation in organic bulk heterojunction (BHJ) devices is key. We found that higher exciton polarizability in BHJ films leads to near-perfect charge generation efficiency.
Area of Science:
- Materials Science
- Organic Electronics
- Photovoltaics
Background:
- The charge generation mechanism in organic bulk heterojunction (BHJ) devices remains incompletely understood.
- Conventional methods struggle to isolate the dielectric properties of electron donors and acceptors in blends, hindering analysis of charge generation efficiencies.
Purpose of the Study:
- To investigate the role of excited state polarizability in organic BHJ devices.
- To correlate molecular properties with charge generation efficiency in BHJ systems.
Main Methods:
- Utilized spectrally resolved electroabsorption spectroscopy.
- Analyzed individual donor and acceptor polarizability in organic blend films.
Main Results:
- Established a direct link between higher exciton polarizability, increased π-π coherence length, and accelerated charge transfer.
- Demonstrated that molecular packing in BHJ films synergistically enhances exciton polarizability.
Conclusions:
- Exciton polarizability is a fundamental factor driving high charge generation efficiency in BHJ devices.
- The findings provide a mechanistic explanation for near-100% charge generation efficiency in BHJ photodiodes.
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