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Charge Separation at Organic Interfaces with Near-Zero Energy Offset: A Step toward Designing Inorganic-like Organic
Neno Fuller1, Kushal Rijal1, Elizabeth Udeh1
1Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States.
The Journal of Physical Chemistry Letters
|November 26, 2025
Summary
Organic semiconductors can achieve charge separation (CS) even with minimal energy offsets at donor-acceptor interfaces. This entropy-driven process in organic photovoltaics avoids voltage loss.
Area of Science:
- Materials Science
- Physical Chemistry
- Organic Electronics
Background:
- Organic semiconductors require energy level offsets at donor-acceptor (D-A) interfaces for charge separation (CS).
- This energy offset causes voltage loss in organic photovoltaics (OPVs).
Purpose of the Study:
- To investigate spontaneous CS at D-A interfaces with minimal energy offsets.
- To explore entropy-driven CS mechanisms in organic semiconductors.
Main Methods:
- Utilized zinc phthalocyanine (ZnPc) and fluorinated zinc phthalocyanine (F4ZnPc) as a model D-A interface.
- Analyzed interfacial energy offsets and charge separation dynamics.
Main Results:
- Spontaneous CS occurred with an enthalpy increase of ~0.3-0.4 eV, despite a small interfacial energy offset of ~0.1 eV.
- The CS process was found to be entropy-driven.
- Entropic driving force was enhanced by point-like wave function contact and small band bending.
Conclusions:
- Effective CS can occur at organic semiconductor interfaces with near-zero energy level offsets.
- This entropy-driven mechanism offers a pathway to avoid energy loss in OPVs.
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