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Interfacial electronic structure of Cl6SubPc non-fullerene acceptors in organic photovoltaics using soft X-ray spectroscopies

Abstract

In organic photovoltaics (OPVs), determining the energy level alignment of a donor and an acceptor is particularly important since the interfacial energy gap between the highest occupied molecular orbital (HOMO) level of a donor and the lowest unoccupied molecular orbital (LUMO) level of an acceptor (EDHOMO-EALUMO) gives the theoretical maximum value of the open-circuit voltage (VOC). To increase the EDHOMO-EALUMO, non-fullerene acceptors, which have a lower electron affinity (EA) than C60, are receiving increased attention. In this study, we investigated the energy level alignment at the interface of a boron chloride subphthalocyanine (SubPc) donor and a halogenated SubPc (Cl6SubPc) acceptor using soft X-ray spectroscopy techniques. The estimated EDHOMO-EALUMO of Cl6SubPc/SubPc was 1.95 eV, which was significantly higher than the 1.51 eV found at the interface of C60/SubPc. This increased EDHOMO-EALUMO was the origin of the enhanced VOC in the OPVs. Additionally, we studied the molecular orientation of Cl6SubPc using angle-dependent X-ray absorption spectroscopy. The highly disordered Cl6SubPc molecules result in low carrier mobility, which would contribute to the lower short-circuit current density of the Cl6SubPc acceptor OPVs than that of the C60 acceptor OPVs.

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Publication details

The article was received on 19 Jul 2017, accepted on 08 Nov 2017 and first published on 09 Nov 2017


Article type: Paper
DOI: 10.1039/C7CP04876A
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Interfacial electronic structure of Cl6SubPc non-fullerene acceptors in organic photovoltaics using soft X-ray spectroscopies

    H. Lee, S. W. Ahn, S. H. Ryu, B. K. Ryu, M. H. Lee, S. W. Cho, K. Smith and T. Jones, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP04876A

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