On the Design of Steep Optical Absorbers for Vacuum‐Processed Organic Solar Cells: One Isopropyl Group Makes…

Abstract

The design of vacuum-processed organic solar cells requires a balance between optimizing energetic and morphological properties for efficient photovoltaic performance. In this study, we investigate two structurally similar molecular donors, DCV-iPr and DCV-Me, which exhibit stark differences in photovoltaic performance despite their minimal chemical differences. Through a combined experimental and theoretical approach-including crystal structure prediction, vapor deposition simulations, GIWAXS measurements, and advanced electronic structure calculations-we establish how molecular packing influences optical absorption and photovoltaic efficiency. Our findings show that steric effects introduced by the isopropyl group in DCV-iPr lead to a brick-wall molecular arrangement, favoring J-like excitonic interactions and resulting in sharp optical absorption with a reduced Stokes shift. In contrast, DCV-Me forms a more H-like aggregation, leading to broadened absorption and higher voltage losses. While DCV-iPr demonstrates enhanced photovoltaic performance, we identify substantial remaining voltage losses associated with charge-transfer excitations at the donor-acceptor interface. This work provides key design guidelines linking molecular packing to optical absorption properties and highlights the need for alternative acceptor materials with steeper absorption onsets to further optimize vacuum-processed organic solar cells.

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BibTeX RIS

BibTeX

@article{bouajhine2026design,
  title = {{On the Design of Steep Optical Absorbers for Vacuum‐Processed Organic Solar Cells: One Isopropyl Group Makes the Difference}},
  author = {Mohamed El Habib Bouajhine and Emilio Lorini and Samuele Giannini and Siebe Frederix and Karsten Walzer and Marieta Levichkova and Gunter Mattersteig and Martin Pfeiffer and Eva Bittrich and Petra Uhlmann and Vincent Lemaur and Koen Vandewal and Patrick Brocorens and Luca Muccioli and David Beljonne},
  journal = {Small Science},
  year = {2026},
  month = may,
  doi = {10.1002/smsc.202500633},
  url = {https://hal.science/hal-05791248v1},
  note = {CC BY},
}

RIS

TY  - JOUR
TI  - On the Design of Steep Optical Absorbers for Vacuum‐Processed Organic Solar Cells: One Isopropyl Group Makes the Difference
AU  - Mohamed El Habib Bouajhine
AU  - Emilio Lorini
AU  - Samuele Giannini
AU  - Siebe Frederix
AU  - Karsten Walzer
AU  - Marieta Levichkova
AU  - Gunter Mattersteig
AU  - Martin Pfeiffer
AU  - Eva Bittrich
AU  - Petra Uhlmann
AU  - Vincent Lemaur
AU  - Koen Vandewal
AU  - Patrick Brocorens
AU  - Luca Muccioli
AU  - David Beljonne
PY  - 2026
DA  - 2026/05/15
JO  - Small Science
DO  - 10.1002/smsc.202500633
UR  - https://hal.science/hal-05791248v1
AB  - The design of vacuum-processed organic solar cells requires a balance between optimizing energetic and morphological properties for efficient photovoltaic performance. In this study, we investigate two structurally similar molecular donors, DCV-iPr and DCV-Me, which exhibit stark differences in photovoltaic performance despite their minimal chemical differences. Through a combined experimental and theoretical approach-including crystal structure prediction, vapor deposition simulations, GIWAXS measurements, and advanced electronic structure calculations-we establish how molecular packing influences optical absorption and photovoltaic efficiency. Our findings show that steric effects introduced by the isopropyl group in DCV-iPr lead to a brick-wall molecular arrangement, favoring J-like excitonic interactions and resulting in sharp optical absorption with a reduced Stokes shift. In contrast, DCV-Me forms a more H-like aggregation, leading to broadened absorption and higher voltage losses. While DCV-iPr demonstrates enhanced photovoltaic performance, we identify substantial remaining voltage losses associated with charge-transfer excitations at the donor-acceptor interface. This work provides key design guidelines linking molecular packing to optical absorption properties and highlights the need for alternative acceptor materials with steeper absorption onsets to further optimize vacuum-processed organic solar cells.
SN  - 2688-4046
ER  -

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