Side-Chain Controlled Exciton Binding Energy in Y-Acceptors Toward Homo-Junction Organic Solar Cells With 5.07%
Haiyun Fan1, Chengyi Xiao1, Haisheng Fang1
1Beijing Advanced Innovation Center for Soft Matter Science and Engineering & State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing, P. R. China.
Small (Weinheim an Der Bergstrasse, Germany)
|December 26, 2025
Summary
Researchers enhanced organic solar cell efficiency by engineering side chains on Y-acceptors. This modification reduced exciton binding energy, leading to a record power conversion efficiency of 5.07% in homo-junction organic solar cells.
Area of Science:
- Organic electronics
- Photovoltaics
- Materials science
Background:
- High exciton binding energy (Eb) limits homo-junction organic solar cell (HJ-OSC) performance.
- Non-fullerene acceptors (e.g., Y-acceptors) have low Eb but suffer from inefficient dissociation and charge transport, capping efficiencies around 4%.
Purpose of the Study:
- To improve HJ-OSC power conversion efficiency (PCE) by reducing exciton binding energy through side-chain engineering.
- To investigate the impact of side-chain structure on molecular packing, polarization, and dielectric permittivity in Y-acceptors.
Main Methods:
- Systematic modification of Y-acceptor alkyl side chains to create three derivatives: Y6-EE, Y6-EH (pristine Y6), and Y6-BO.
- Fabrication and characterization of HJ-OSCs using these Y-acceptor derivatives.
- Analysis of molecular packing, polarization, and dielectric permittivity influenced by side-chain structure.
Main Results:
- The Y6-EE derivative, featuring a compact 2-ethylethyl side chain, demonstrated denser molecular packing, enhanced polarization, and increased dielectric permittivity.
- These effects in Y6-EE led to a reduced Eb and accelerated charge generation kinetics.
- Y6-EE based HJ-OSCs achieved a record PCE of 5.07% and a short-circuit current density (JSC) of 10.62 mA/cm², significantly outperforming Y6-EH and Y6-BO based devices.
Conclusions:
- Side-chain topology critically influences exciton binding energy and charge generation efficiency in HJ-OSCs.
- Molecular design strategies focusing on side-chain engineering can unlock higher performance in organic solar cells.
- Achieved record PCE of 5.07% demonstrates the potential of Y-acceptor based HJ-OSCs.
Keywords:
Y‐acceptorsexciton binding energyhomo‐junction organic solar cellspower conversion efficiencyside‐chain engineeringMore Related Videos
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