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Hydrogenated under-stoichiometric tungsten oxide anode interlayers for efficient and stable organic photovoltaics

Hydrogenated under-stoichiometric tungsten oxide anode interlayers for efficient and stable organic photovoltaics
Hydrogenated under-stoichiometric tungsten oxide anode interlayers for efficient and stable organic photovoltaics

In this work a hydrogenated under-stoichiometric tungsten oxide is introduced as an efficient anode interlayer in organic photovoltaics (OPVs). The benefits of hydrogen incorporation into the oxide lattice for obtaining desirable properties of tungsten oxides are explored. These benefits include the occupation of gap states near the Fermi level, which may facilitate charge transport, and the maintenance of a high work function, nearly similar to that of the stoichiometric tungsten oxide, which contributes to the formation of a large interfacial dipole at the anode interface and enhances charge extraction. A large improvement was achieved in the operational characteristics-especially in the open-circuit voltage-of bulk heterojunction solar cells based on different polymeric donors, namely poly(3-hexylthiophene), P3HT, or poly[(9-(1-octylnonyl)-9H-carbazole-2,7-diyl)-2,5-thiophenediyl-2,1, 3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl], PCDTBT, and the fullerene acceptor [6,6]-phenyl-C71 butyric acid methyl ester, PC 71BM, that incorporated a hydrogenated tungsten oxide as an anode interlayer. This improvement was correlated with the devices' incident photon-to-electron conversion efficiencies (IPCEs) and impedance measurements. Furthermore, an increase in both the device's flat-band voltage (Vfb) and the doping level of the organic semiconductor was measured in P3HT:PC 71BM based devices by Mott-Schottky capacitance analysis. Additional benefits are the large process window established for the devices incorporating the hydrogenated tungsten oxide as an anode interlayer and the maintenance of a high PCE (>80% of its initial efficiency) over 50 days, demonstrating good long-term stability, which is much better than that of the conventional devices based on PEDOT:PSS. The results suggest that the interface engineering with hydrogen-treated metal oxide interlayers is an important strategy to develop highly performing and stable organic photovoltaics.

2050-7488
1738-1749
Vasilopoulou, M.
aad1381e-d091-4090-8c7c-b74bed22393d
Soultati, A.
75205fde-50fc-473e-ad72-ab0b3c6b2cb9
Georgiadou, D. G.
84977176-3678-4fb3-a3dd-2044a49c853b
Stergiopoulos, T.
f00291bb-5ff8-4b4e-a391-3acce0303f78
Palilis, L. C.
b09e9554-54da-4be5-aa08-bda894e2b86f
Kennou, S.
7ca6a6bd-6a05-4110-b3da-c8807f798370
Stathopoulos, N. A.
83a4653f-c4c8-464a-8ed1-a93c52cf3833
Davazoglou, D.
a946cf5d-287a-4734-ba55-b180ab4525ed
Argitis, P.
ab9c4ea6-3dd2-4e34-935d-81bfb360f358
Vasilopoulou, M.
aad1381e-d091-4090-8c7c-b74bed22393d
Soultati, A.
75205fde-50fc-473e-ad72-ab0b3c6b2cb9
Georgiadou, D. G.
84977176-3678-4fb3-a3dd-2044a49c853b
Stergiopoulos, T.
f00291bb-5ff8-4b4e-a391-3acce0303f78
Palilis, L. C.
b09e9554-54da-4be5-aa08-bda894e2b86f
Kennou, S.
7ca6a6bd-6a05-4110-b3da-c8807f798370
Stathopoulos, N. A.
83a4653f-c4c8-464a-8ed1-a93c52cf3833
Davazoglou, D.
a946cf5d-287a-4734-ba55-b180ab4525ed
Argitis, P.
ab9c4ea6-3dd2-4e34-935d-81bfb360f358

Vasilopoulou, M., Soultati, A., Georgiadou, D. G., Stergiopoulos, T., Palilis, L. C., Kennou, S., Stathopoulos, N. A., Davazoglou, D. and Argitis, P. (2014) Hydrogenated under-stoichiometric tungsten oxide anode interlayers for efficient and stable organic photovoltaics. Journal of Materials Chemistry A, 2 (6), 1738-1749. (doi:10.1039/c3ta13975a).

Record type: Article

Abstract

In this work a hydrogenated under-stoichiometric tungsten oxide is introduced as an efficient anode interlayer in organic photovoltaics (OPVs). The benefits of hydrogen incorporation into the oxide lattice for obtaining desirable properties of tungsten oxides are explored. These benefits include the occupation of gap states near the Fermi level, which may facilitate charge transport, and the maintenance of a high work function, nearly similar to that of the stoichiometric tungsten oxide, which contributes to the formation of a large interfacial dipole at the anode interface and enhances charge extraction. A large improvement was achieved in the operational characteristics-especially in the open-circuit voltage-of bulk heterojunction solar cells based on different polymeric donors, namely poly(3-hexylthiophene), P3HT, or poly[(9-(1-octylnonyl)-9H-carbazole-2,7-diyl)-2,5-thiophenediyl-2,1, 3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl], PCDTBT, and the fullerene acceptor [6,6]-phenyl-C71 butyric acid methyl ester, PC 71BM, that incorporated a hydrogenated tungsten oxide as an anode interlayer. This improvement was correlated with the devices' incident photon-to-electron conversion efficiencies (IPCEs) and impedance measurements. Furthermore, an increase in both the device's flat-band voltage (Vfb) and the doping level of the organic semiconductor was measured in P3HT:PC 71BM based devices by Mott-Schottky capacitance analysis. Additional benefits are the large process window established for the devices incorporating the hydrogenated tungsten oxide as an anode interlayer and the maintenance of a high PCE (>80% of its initial efficiency) over 50 days, demonstrating good long-term stability, which is much better than that of the conventional devices based on PEDOT:PSS. The results suggest that the interface engineering with hydrogen-treated metal oxide interlayers is an important strategy to develop highly performing and stable organic photovoltaics.

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More information

Accepted/In Press date: 9 November 2013
e-pub ahead of print date: 11 November 2013
Published date: 14 February 2014

Identifiers

Local EPrints ID: 440498
URI: http://eprints.soton.ac.uk/id/eprint/440498
ISSN: 2050-7488
PURE UUID: 02a3e337-f542-4636-8e4f-9c86ccd7d601
ORCID for D. G. Georgiadou: ORCID iD orcid.org/0000-0002-2620-3346

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Date deposited: 05 May 2020 16:42
Last modified: 07 Oct 2020 02:27

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Contributors

Author: M. Vasilopoulou
Author: A. Soultati
Author: T. Stergiopoulos
Author: L. C. Palilis
Author: S. Kennou
Author: N. A. Stathopoulos
Author: D. Davazoglou
Author: P. Argitis

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