Sputter Deposited TiOx Thin-Films as Electron Transport Layers in Organic Solar Cells

Mina Mirsafaei, Pia Bomholt Jensen, Harish Lakhotiya, John Lundsgaard Hansen, Sanjay Ram, Brian Julsgaard, Peter Balling, Horst-Günter Rubahn, Morten Madsen

Research output: Contribution to conference without publisher/journalPosterResearchpeer-review

Abstract

The use of interfacial layers in organic solar cells has been investigated intensively over the past years, as it has a strong impact on both the power conversion efficiency and stability of the devices. Among the systems investigated are for example alkali salts, ionic liquids, neutral polymers, conjugated polyelectrolytes and various metal-oxides, which have been demonstrated to result in promising device characteristics1. In this context, n-type metal-oxides such as titanium oxide (TiOx) have drawn a lot of attention as electron-transport and exciton-blocking layers, mainly due to its high optical transparency and favorable energy-level alignment with many commonly used electron-acceptor materials.
There are several methods available for fabricating compact TiOx thin-films for use in organic solar cells, including sol-gel solution processing, spray pyrolysis and atomic-layer deposition; however, these methods either require sintering at high temperatures, or result in the existence of trapped sites in the films, which lead to the presence of the well-known s-shape in the J-V curves of the devices. In order to remove the observed s-shape, and thus improve the fill factor of the cells, light soaking is typically performed, which however brings along several unwanted side-effects in terms of energy losses, material degradation, batch-to-batch variations, etc.2
In this work, we demonstrate the development of TiOx based light-soaking-free inverted polymer solar cells with power conversion efficiency of around 7%, by incorporating sputter deposited TiOx thin-films as electron-transport and exciton-blocking layers. In the work, we report on the effect of different TiOx deposition temperatures and thicknesses on the organic-solar-cell device performance. Besides optical characterization, AFM and XRD analyses are performed to characterize the morphology and crystal structure of the films, and external quantum efficiency measurements are employed to shed further light on the device performance. Our study presents a novel method for implementation of TiOx thin-films as electron-transport layer in organic solar cells that eliminates the need for light soaking and still allows for integration on flexible plastic substrates, which is beneficial for roll-to-roll mass production of flexible organic solar cells.

1. Steim, R.; Kogler, F. R.; Brabec, C. J., Interface materials for organic solar cells. Journal of Materials Chemistry 2010, 20 (13), 2499-2512.
2. Kim, J.; Kim, G.; Choi, Y.; Lee, J.; Park, S. H.; Lee, K., Light-soaking issue in polymer solar cells: Photoinduced energy level alignment at the sol-gel processed metal oxide and indium tin oxide interface. Journal of Applied Physics 2012, 111 (11), 114511.

Original languageEnglish
Publication date21. May 2017
Publication statusPublished - 21. May 2017
EventInternational Conference on Hybrid and Organic Photovoltaics - Lausanne, Switzerland
Duration: 21. May 201724. May 2017
http://nanoge.org/HOPV17/

Conference

ConferenceInternational Conference on Hybrid and Organic Photovoltaics
CountrySwitzerland
CityLausanne
Period21/05/201724/05/2017
Internet address

Fingerprint

titanium oxides
solar cells
soaking
thin films
electrons
metal oxides
polymers
energy levels
alignment
acceptor materials
excitons
gels
atomic layer epitaxy
indium oxides
tin oxides
pyrolysis
sprayers
quantum efficiency
alkalies
sintering

Cite this

Mirsafaei, M., Bomholt Jensen, P., Lakhotiya, H., Lundsgaard Hansen, J., Ram, S., Julsgaard, B., ... Madsen, M. (2017). Sputter Deposited TiOx Thin-Films as Electron Transport Layers in Organic Solar Cells. Poster session presented at International Conference on Hybrid and Organic Photovoltaics, Lausanne, Switzerland.
Mirsafaei, Mina ; Bomholt Jensen, Pia ; Lakhotiya, Harish ; Lundsgaard Hansen, John ; Ram, Sanjay ; Julsgaard, Brian ; Balling, Peter ; Rubahn, Horst-Günter ; Madsen, Morten. / Sputter Deposited TiOx Thin-Films as Electron Transport Layers in Organic Solar Cells. Poster session presented at International Conference on Hybrid and Organic Photovoltaics, Lausanne, Switzerland.
@conference{4cd8130b2fda4149a1844b3fb19a17f5,
title = "Sputter Deposited TiOx Thin-Films as Electron Transport Layers in Organic Solar Cells",
abstract = "The use of interfacial layers in organic solar cells has been investigated intensively over the past years, as it has a strong impact on both the power conversion efficiency and stability of the devices. Among the systems investigated are for example alkali salts, ionic liquids, neutral polymers, conjugated polyelectrolytes and various metal-oxides, which have been demonstrated to result in promising device characteristics1. In this context, n-type metal-oxides such as titanium oxide (TiOx) have drawn a lot of attention as electron-transport and exciton-blocking layers, mainly due to its high optical transparency and favorable energy-level alignment with many commonly used electron-acceptor materials. There are several methods available for fabricating compact TiOx thin-films for use in organic solar cells, including sol-gel solution processing, spray pyrolysis and atomic-layer deposition; however, these methods either require sintering at high temperatures, or result in the existence of trapped sites in the films, which lead to the presence of the well-known s-shape in the J-V curves of the devices. In order to remove the observed s-shape, and thus improve the fill factor of the cells, light soaking is typically performed, which however brings along several unwanted side-effects in terms of energy losses, material degradation, batch-to-batch variations, etc.2In this work, we demonstrate the development of TiOx based light-soaking-free inverted polymer solar cells with power conversion efficiency of around 7{\%}, by incorporating sputter deposited TiOx thin-films as electron-transport and exciton-blocking layers. In the work, we report on the effect of different TiOx deposition temperatures and thicknesses on the organic-solar-cell device performance. Besides optical characterization, AFM and XRD analyses are performed to characterize the morphology and crystal structure of the films, and external quantum efficiency measurements are employed to shed further light on the device performance. Our study presents a novel method for implementation of TiOx thin-films as electron-transport layer in organic solar cells that eliminates the need for light soaking and still allows for integration on flexible plastic substrates, which is beneficial for roll-to-roll mass production of flexible organic solar cells. 1. Steim, R.; Kogler, F. R.; Brabec, C. J., Interface materials for organic solar cells. Journal of Materials Chemistry 2010, 20 (13), 2499-2512.2. Kim, J.; Kim, G.; Choi, Y.; Lee, J.; Park, S. H.; Lee, K., Light-soaking issue in polymer solar cells: Photoinduced energy level alignment at the sol-gel processed metal oxide and indium tin oxide interface. Journal of Applied Physics 2012, 111 (11), 114511.",
author = "Mina Mirsafaei and {Bomholt Jensen}, Pia and Harish Lakhotiya and {Lundsgaard Hansen}, John and Sanjay Ram and Brian Julsgaard and Peter Balling and Horst-G{\"u}nter Rubahn and Morten Madsen",
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language = "English",
note = "International Conference on Hybrid and Organic Photovoltaics, HOPV 2017 ; Conference date: 21-05-2017 Through 24-05-2017",
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}

Mirsafaei, M, Bomholt Jensen, P, Lakhotiya, H, Lundsgaard Hansen, J, Ram, S, Julsgaard, B, Balling, P, Rubahn, H-G & Madsen, M 2017, 'Sputter Deposited TiOx Thin-Films as Electron Transport Layers in Organic Solar Cells', International Conference on Hybrid and Organic Photovoltaics, Lausanne, Switzerland, 21/05/2017 - 24/05/2017.

Sputter Deposited TiOx Thin-Films as Electron Transport Layers in Organic Solar Cells. / Mirsafaei, Mina; Bomholt Jensen, Pia; Lakhotiya, Harish ; Lundsgaard Hansen, John; Ram, Sanjay; Julsgaard, Brian; Balling, Peter; Rubahn, Horst-Günter; Madsen, Morten.

2017. Poster session presented at International Conference on Hybrid and Organic Photovoltaics, Lausanne, Switzerland.

Research output: Contribution to conference without publisher/journalPosterResearchpeer-review

TY - CONF

T1 - Sputter Deposited TiOx Thin-Films as Electron Transport Layers in Organic Solar Cells

AU - Mirsafaei, Mina

AU - Bomholt Jensen, Pia

AU - Lakhotiya, Harish

AU - Lundsgaard Hansen, John

AU - Ram, Sanjay

AU - Julsgaard, Brian

AU - Balling, Peter

AU - Rubahn, Horst-Günter

AU - Madsen, Morten

PY - 2017/5/21

Y1 - 2017/5/21

N2 - The use of interfacial layers in organic solar cells has been investigated intensively over the past years, as it has a strong impact on both the power conversion efficiency and stability of the devices. Among the systems investigated are for example alkali salts, ionic liquids, neutral polymers, conjugated polyelectrolytes and various metal-oxides, which have been demonstrated to result in promising device characteristics1. In this context, n-type metal-oxides such as titanium oxide (TiOx) have drawn a lot of attention as electron-transport and exciton-blocking layers, mainly due to its high optical transparency and favorable energy-level alignment with many commonly used electron-acceptor materials. There are several methods available for fabricating compact TiOx thin-films for use in organic solar cells, including sol-gel solution processing, spray pyrolysis and atomic-layer deposition; however, these methods either require sintering at high temperatures, or result in the existence of trapped sites in the films, which lead to the presence of the well-known s-shape in the J-V curves of the devices. In order to remove the observed s-shape, and thus improve the fill factor of the cells, light soaking is typically performed, which however brings along several unwanted side-effects in terms of energy losses, material degradation, batch-to-batch variations, etc.2In this work, we demonstrate the development of TiOx based light-soaking-free inverted polymer solar cells with power conversion efficiency of around 7%, by incorporating sputter deposited TiOx thin-films as electron-transport and exciton-blocking layers. In the work, we report on the effect of different TiOx deposition temperatures and thicknesses on the organic-solar-cell device performance. Besides optical characterization, AFM and XRD analyses are performed to characterize the morphology and crystal structure of the films, and external quantum efficiency measurements are employed to shed further light on the device performance. Our study presents a novel method for implementation of TiOx thin-films as electron-transport layer in organic solar cells that eliminates the need for light soaking and still allows for integration on flexible plastic substrates, which is beneficial for roll-to-roll mass production of flexible organic solar cells. 1. Steim, R.; Kogler, F. R.; Brabec, C. J., Interface materials for organic solar cells. Journal of Materials Chemistry 2010, 20 (13), 2499-2512.2. Kim, J.; Kim, G.; Choi, Y.; Lee, J.; Park, S. H.; Lee, K., Light-soaking issue in polymer solar cells: Photoinduced energy level alignment at the sol-gel processed metal oxide and indium tin oxide interface. Journal of Applied Physics 2012, 111 (11), 114511.

AB - The use of interfacial layers in organic solar cells has been investigated intensively over the past years, as it has a strong impact on both the power conversion efficiency and stability of the devices. Among the systems investigated are for example alkali salts, ionic liquids, neutral polymers, conjugated polyelectrolytes and various metal-oxides, which have been demonstrated to result in promising device characteristics1. In this context, n-type metal-oxides such as titanium oxide (TiOx) have drawn a lot of attention as electron-transport and exciton-blocking layers, mainly due to its high optical transparency and favorable energy-level alignment with many commonly used electron-acceptor materials. There are several methods available for fabricating compact TiOx thin-films for use in organic solar cells, including sol-gel solution processing, spray pyrolysis and atomic-layer deposition; however, these methods either require sintering at high temperatures, or result in the existence of trapped sites in the films, which lead to the presence of the well-known s-shape in the J-V curves of the devices. In order to remove the observed s-shape, and thus improve the fill factor of the cells, light soaking is typically performed, which however brings along several unwanted side-effects in terms of energy losses, material degradation, batch-to-batch variations, etc.2In this work, we demonstrate the development of TiOx based light-soaking-free inverted polymer solar cells with power conversion efficiency of around 7%, by incorporating sputter deposited TiOx thin-films as electron-transport and exciton-blocking layers. In the work, we report on the effect of different TiOx deposition temperatures and thicknesses on the organic-solar-cell device performance. Besides optical characterization, AFM and XRD analyses are performed to characterize the morphology and crystal structure of the films, and external quantum efficiency measurements are employed to shed further light on the device performance. Our study presents a novel method for implementation of TiOx thin-films as electron-transport layer in organic solar cells that eliminates the need for light soaking and still allows for integration on flexible plastic substrates, which is beneficial for roll-to-roll mass production of flexible organic solar cells. 1. Steim, R.; Kogler, F. R.; Brabec, C. J., Interface materials for organic solar cells. Journal of Materials Chemistry 2010, 20 (13), 2499-2512.2. Kim, J.; Kim, G.; Choi, Y.; Lee, J.; Park, S. H.; Lee, K., Light-soaking issue in polymer solar cells: Photoinduced energy level alignment at the sol-gel processed metal oxide and indium tin oxide interface. Journal of Applied Physics 2012, 111 (11), 114511.

M3 - Poster

ER -

Mirsafaei M, Bomholt Jensen P, Lakhotiya H, Lundsgaard Hansen J, Ram S, Julsgaard B et al. Sputter Deposited TiOx Thin-Films as Electron Transport Layers in Organic Solar Cells. 2017. Poster session presented at International Conference on Hybrid and Organic Photovoltaics, Lausanne, Switzerland.