Adjusting the energy of interfacial states in organic photovoltaics for maximum efficiency

Nicola Gasparini, Franco V. A. Camargo, Stefan Frühwald, Tetsuhiko Nagahara, Andrej Classen, Steffen Roland, Andrew Wadsworth, Vasilis G. Gregoriou, Christos L. Chochos, Dieter Neher, Michael Salvador, Derya Baran, Iain McCulloch, Andreas Görling, Larry Lüer, Giulio Cerullo, Christoph J. Brabec

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


AbstractA critical bottleneck for improving the performance of organic solar cells (OSC) is minimising non-radiative losses in the interfacial charge-transfer (CT) state via the formation of hybrid energetic states. This requires small energetic offsets often detrimental for high external quantum efficiency (EQE). Here, we obtain OSC with both non-radiative voltage losses (0.24 V) and photocurrent losses (EQE > 80%) simultaneously minimised. The interfacial CT states separate into free carriers with ≈40-ps time constant. We combine device and spectroscopic data to model the thermodynamics of charge separation and extraction, revealing that the relatively high performance of the devices arises from an optimal adjustment of the CT state energy, which determines how the available overall driving force is efficiently used to maximize both exciton splitting and charge separation. The model proposed is universal for donor:acceptor (D:A) with low driving forces and predicts which D:A will benefit from a morphology optimization for highly efficient OSC.
Original languageEnglish (US)
JournalNature Communications
Issue number1
StatePublished - Mar 19 2021

Bibliographical note

KAUST Repository Item: Exported on 2021-03-22
Acknowledgements: N.G. acknowledges the Imperial College Research Fellowship scheme. C.J.B. gratefully acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), Project no. 182849149-SFB 953. C.J.B. gratefully acknowledges financial support through the “Aufbruch Bayern” initiative of the state of Bavaria (EnCN and SFF) and the Bavarian Initiative “Solar Technologies go Hybrid” (SolTech) and funding from DFG project DFG INST 90/917. C.C.L. thanks the European Union for the financial support. G.C. acknowledges the support from the PRIN 2017 Project 201795SBA3—HARVEST.

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Chemistry
  • General Physics and Astronomy


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