Open-circuit voltage of organic solar cells: interfacial roughness makes the difference

Carl Poelking, Johannes Benduhn, Donato Spoltore, Martin Schwarze, Steffen Roland, Fortunato Piersimoni, Dieter Neher, Karl Leo, Koen Vandewal, Denis Andrienko

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Organic photovoltaics (PV) is an energy-harvesting technology that offers many advantages, such as flexibility, low weight and cost, as well as environmentally benign materials and manufacturing techniques. Despite growth of power conversion efficiencies to around 19 % in the last years, organic PVs still lag behind inorganic PV technologies, mainly due to high losses in open-circuit voltage. Understanding and improving open circuit voltage in organic solar cells is challenging, as it is controlled by the properties of a donor-acceptor interface where the optical excitations are separated into charge carriers. Here, we provide an electrostatic model of a rough donor-acceptor interface and test it experimentally on small molecule PV materials systems. The model provides concise relationships between the open-circuit voltage, photovoltaic gap, charge-transfer state energy, and interfacial morphology. In particular, we show that the electrostatic bias generated across the interface reduces the photovoltaic gap. This negative influence on open-circuit voltage can, however, be circumvented by adjusting the morphology of the donor-acceptor interface.
Original languageEnglish (US)
JournalCommunications Physics
Issue number1
StatePublished - Nov 29 2022
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2022-12-01
Acknowledged KAUST grant number(s): OSR-2018-CARF/CCF-3079, OSR-CRG2018-3746
Acknowledgements: Open Access funding enabled and organized by Projekt DEAL. This publication is based on work supported by the KAUST Office of Sponsored Research (OSR) under award nos. OSR-2018-CARF/CCF-3079 and OSR-CRG2018-3746. D.A. also acknowledges the KAUST PSE Division for hosting his sabbatical in the framework of the Division’s Visiting Faculty program. D.A. acknowledges funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) for financial support through the collaborative research centers TRR 146, SPP 2196, and grant number 460766640. We thank Kun-Han Lin, Leanne Paterson, Wenlan Liu, Mukunda Mandal, and Naomi Kinaret for fruitful discussions and proof reading of the manuscript. Furthermore, the authors acknowledge Dr. Beatrice Beyer from Fraunhofer Institut FEP for supplying the donor molecule ZnF4Pc. J.B. and K.L. acknowledge the German Federal Ministry of Education and Research (BMBF) for funding through the projects “Pergamon” (16ME0012) and “Flexmonirs” (01DR20008A).
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


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