The University of Southampton
University of Southampton Institutional Repository

Deducing transport properties of mobile vacancies from perovskite solar cell characteristics

Deducing transport properties of mobile vacancies from perovskite solar cell characteristics
Deducing transport properties of mobile vacancies from perovskite solar cell characteristics

The absorber layers in perovskite solar cells possess a high concentration of mobile ion vacancies. These vacancies undertake thermally activated hops between neighboring lattice sites. The mobile vacancy concentration N 0 is much higher and the activation energy E A for ion hops is much lower than is seen in most other semiconductors due to the inherent softness of perovskite materials. The timescale at which the internal electric field changes due to ion motion is determined by the vacancy diffusion coefficient D v and is similar to the timescale on which the external bias changes by a significant fraction of the open-circuit voltage at typical scan rates. Therefore, hysteresis is often observed in which the shape of the current-voltage, J-V, characteristic depends on the direction of the voltage sweep. There is also evidence that this defect migration plays a role in degradation. By employing a charge transport model of coupled ion-electron conduction in a perovskite solar cell, we show that E A for the ion species responsible for hysteresis can be obtained directly from measurements of the temperature variation of the scan-rate dependence of the short-circuit current and of the hysteresis factor H. This argument is validated by comparing E A deduced from measured J-V curves for four solar cell structures with density functional theory calculations. In two of these structures, the perovskite is MAPbI 3, where MA is methylammonium, CH 3 NH 3; the hole transport layer (HTL) is spiro (spiro-OMeTAD, 2,2 ′,7,7 ′- tetrakis[N,N-di(4-methoxyphenyl) amino]-9,9 ′-spirobifluorene) and the electron transport layer (ETL) is TiO 2 or SnO 2. For the third and fourth structures, the perovskite layer is FAPbI 3, where FA is formamidinium, HC (NH 2) 2, or MAPbBr 3, and in both cases, the HTL is spiro and the ETL is SnO 2. For all four structures, the hole and electron extracting electrodes are Au and fluorine doped tin oxide, respectively. We also use our model to predict how the scan rate dependence of the power conversion efficiency varies with E A, N 0, and parameters determining free charge recombination.

0021-8979
Cave, James M.
a1036cfa-7f83-45e9-9543-58111dea690d
Courtier, Nicola E.
754366ef-0f5b-4bf0-a411-edcc159cd483
Blakborn, Isabelle A.
056d98ef-1df9-4832-9288-6103d64eba4d
Jones, Timothy W.
492fcc23-2c49-4258-afe1-48c15d1c39f1
Ghosh, Dibyajyoti
abf96943-fbd1-47f8-939b-256491347e68
Anderson, Kenrick F.
4db1e9c5-839f-4d2b-8240-6efbdce484b5
Lin, Liangyou
aeb9efd0-db24-4dca-8b30-a866a8b28b2d
Dijkhoff, Andrew A.
376a18f7-3424-44bd-b19f-63804f84baec
Wilson, Gregory J.
6cbba852-8a15-4a33-a509-d45a7b532a14
Feron, Krishna
f5454cbc-2174-4288-b327-6da5ae26e23b
Saiful Islam, M.
9b63ca9e-7d6e-49ab-976e-6c3c417b2466
Foster, Jamie M.
0786436b-150f-4b67-bd8c-126dbfce76bb
Richardson, Giles
3fd8e08f-e615-42bb-a1ff-3346c5847b91
Walker, Alison B.
c3875e6c-168f-43da-b938-04164dd9e2e4
Cave, James M.
a1036cfa-7f83-45e9-9543-58111dea690d
Courtier, Nicola E.
754366ef-0f5b-4bf0-a411-edcc159cd483
Blakborn, Isabelle A.
056d98ef-1df9-4832-9288-6103d64eba4d
Jones, Timothy W.
492fcc23-2c49-4258-afe1-48c15d1c39f1
Ghosh, Dibyajyoti
abf96943-fbd1-47f8-939b-256491347e68
Anderson, Kenrick F.
4db1e9c5-839f-4d2b-8240-6efbdce484b5
Lin, Liangyou
aeb9efd0-db24-4dca-8b30-a866a8b28b2d
Dijkhoff, Andrew A.
376a18f7-3424-44bd-b19f-63804f84baec
Wilson, Gregory J.
6cbba852-8a15-4a33-a509-d45a7b532a14
Feron, Krishna
f5454cbc-2174-4288-b327-6da5ae26e23b
Saiful Islam, M.
9b63ca9e-7d6e-49ab-976e-6c3c417b2466
Foster, Jamie M.
0786436b-150f-4b67-bd8c-126dbfce76bb
Richardson, Giles
3fd8e08f-e615-42bb-a1ff-3346c5847b91
Walker, Alison B.
c3875e6c-168f-43da-b938-04164dd9e2e4

Cave, James M., Courtier, Nicola E., Blakborn, Isabelle A., Jones, Timothy W., Ghosh, Dibyajyoti, Anderson, Kenrick F., Lin, Liangyou, Dijkhoff, Andrew A., Wilson, Gregory J., Feron, Krishna, Saiful Islam, M., Foster, Jamie M., Richardson, Giles and Walker, Alison B. (2020) Deducing transport properties of mobile vacancies from perovskite solar cell characteristics. Journal of Applied Physics, 128 (18), [184501]. (doi:10.1063/5.0021849).

Record type: Article

Abstract

The absorber layers in perovskite solar cells possess a high concentration of mobile ion vacancies. These vacancies undertake thermally activated hops between neighboring lattice sites. The mobile vacancy concentration N 0 is much higher and the activation energy E A for ion hops is much lower than is seen in most other semiconductors due to the inherent softness of perovskite materials. The timescale at which the internal electric field changes due to ion motion is determined by the vacancy diffusion coefficient D v and is similar to the timescale on which the external bias changes by a significant fraction of the open-circuit voltage at typical scan rates. Therefore, hysteresis is often observed in which the shape of the current-voltage, J-V, characteristic depends on the direction of the voltage sweep. There is also evidence that this defect migration plays a role in degradation. By employing a charge transport model of coupled ion-electron conduction in a perovskite solar cell, we show that E A for the ion species responsible for hysteresis can be obtained directly from measurements of the temperature variation of the scan-rate dependence of the short-circuit current and of the hysteresis factor H. This argument is validated by comparing E A deduced from measured J-V curves for four solar cell structures with density functional theory calculations. In two of these structures, the perovskite is MAPbI 3, where MA is methylammonium, CH 3 NH 3; the hole transport layer (HTL) is spiro (spiro-OMeTAD, 2,2 ′,7,7 ′- tetrakis[N,N-di(4-methoxyphenyl) amino]-9,9 ′-spirobifluorene) and the electron transport layer (ETL) is TiO 2 or SnO 2. For the third and fourth structures, the perovskite layer is FAPbI 3, where FA is formamidinium, HC (NH 2) 2, or MAPbBr 3, and in both cases, the HTL is spiro and the ETL is SnO 2. For all four structures, the hole and electron extracting electrodes are Au and fluorine doped tin oxide, respectively. We also use our model to predict how the scan rate dependence of the power conversion efficiency varies with E A, N 0, and parameters determining free charge recombination.

Text
JAP20-AR-04499 - Accepted Manuscript
Download (4MB)

More information

Accepted/In Press date: 16 October 2020
e-pub ahead of print date: 9 November 2020
Published date: 14 November 2020

Identifiers

Local EPrints ID: 445793
URI: http://eprints.soton.ac.uk/id/eprint/445793
ISSN: 0021-8979
PURE UUID: 033b6a40-7117-47dc-af04-fc97f43d6bbd
ORCID for Nicola E. Courtier: ORCID iD orcid.org/0000-0002-5714-1096
ORCID for Giles Richardson: ORCID iD orcid.org/0000-0001-6225-8590

Catalogue record

Date deposited: 07 Jan 2021 17:34
Last modified: 17 Mar 2024 03:17

Export record

Altmetrics

Contributors

Author: James M. Cave
Author: Nicola E. Courtier ORCID iD
Author: Isabelle A. Blakborn
Author: Timothy W. Jones
Author: Dibyajyoti Ghosh
Author: Kenrick F. Anderson
Author: Liangyou Lin
Author: Andrew A. Dijkhoff
Author: Gregory J. Wilson
Author: Krishna Feron
Author: M. Saiful Islam
Author: Jamie M. Foster
Author: Alison B. Walker

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×