Issue 47, 2017

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 (EDHOMOEALUMO) gives the theoretical maximum value of the open-circuit voltage (VOC). To increase the EDHOMOEALUMO, non-fullerene acceptors, which have a lower electron affinity (EA) than C60, are receiving increasing 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 EDHOMOEALUMO of Cl6SubPc/SubPc was 1.95 eV, which was significantly higher than that of 1.51 eV found at the interface of C60/SubPc. This increased EDHOMOEALUMO was the origin of the enhanced VOC in 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 contributes to the lower short-circuit current density of the Cl6SubPc acceptor OPVs than the C60 acceptor OPVs.

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

Article information

Article type
Paper
Submitted
19 Jul 2017
Accepted
08 Nov 2017
First published
09 Nov 2017

Phys. Chem. Chem. Phys., 2017,19, 31628-31633

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. E. Smith and T. S. Jones, Phys. Chem. Chem. Phys., 2017, 19, 31628 DOI: 10.1039/C7CP04876A

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