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Interpreting ideality factors for planar perovskite solar cells: ectypal diode theory for steady-state operation

Interpreting ideality factors for planar perovskite solar cells: ectypal diode theory for steady-state operation
Interpreting ideality factors for planar perovskite solar cells: ectypal diode theory for steady-state operation
Ideality factors are used to identify the dominant form of recombination in many types of solar cell and guide future development. Unusual non-integer and voltage-dependent ideality factors, which are difficult to explain using the classical diode theory, have been reported for perovskite solar cells and remain unexplained. Experimental measurements and theoretical simulations of the electric potential profile across a planar perovskite solar cell show that significant potential drops occur across each of the perovskite/transport layer interfaces. Such potential profiles are fundamentally distinct from the single potential drop that characterises a p-n or a p-i-n junction. We propose an analytical model, developed specifically for perovskite devices, in which the ideality factor is replaced by a systematically derived analogue which we term the ectypal factor. In common with the classical theory, the ectypal diode equation is derived as an approximation to a drift-diffusion model for the motion of charges across a solar cell however, crucially, it incorporates the effects of ion migration within the perovskite absorber layer. The theory provides a framework for analysing the steady-state performance of a perovskite solar cell according to the value of the ectypal factor. Predictions are verified against numerical simulations of a full set of drift-diffusion equations. An important conclusion is that our ability to evaluate PSC performance, using standard techniques such as the analysis of dark J-V or Suns-Voc measurements, relies on understanding how the potential distribution varies with applied voltage. Implications of this work on the interpretation of data from the literature are discussed.
2331-7019
024031
Courtier, Nicola
754366ef-0f5b-4bf0-a411-edcc159cd483
Courtier, Nicola
754366ef-0f5b-4bf0-a411-edcc159cd483

Courtier, Nicola (2020) Interpreting ideality factors for planar perovskite solar cells: ectypal diode theory for steady-state operation. Physical Review Applied, 14 (2), 024031, [024031]. (doi:10.1103/PhysRevApplied.14.024031).

Record type: Article

Abstract

Ideality factors are used to identify the dominant form of recombination in many types of solar cell and guide future development. Unusual non-integer and voltage-dependent ideality factors, which are difficult to explain using the classical diode theory, have been reported for perovskite solar cells and remain unexplained. Experimental measurements and theoretical simulations of the electric potential profile across a planar perovskite solar cell show that significant potential drops occur across each of the perovskite/transport layer interfaces. Such potential profiles are fundamentally distinct from the single potential drop that characterises a p-n or a p-i-n junction. We propose an analytical model, developed specifically for perovskite devices, in which the ideality factor is replaced by a systematically derived analogue which we term the ectypal factor. In common with the classical theory, the ectypal diode equation is derived as an approximation to a drift-diffusion model for the motion of charges across a solar cell however, crucially, it incorporates the effects of ion migration within the perovskite absorber layer. The theory provides a framework for analysing the steady-state performance of a perovskite solar cell according to the value of the ectypal factor. Predictions are verified against numerical simulations of a full set of drift-diffusion equations. An important conclusion is that our ability to evaluate PSC performance, using standard techniques such as the analysis of dark J-V or Suns-Voc measurements, relies on understanding how the potential distribution varies with applied voltage. Implications of this work on the interpretation of data from the literature are discussed.

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Phys Rev Applied 14.024031 - Version of Record
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Accepted/In Press date: 10 July 2020
Published date: 12 August 2020

Identifiers

Local EPrints ID: 443042
URI: http://eprints.soton.ac.uk/id/eprint/443042
ISSN: 2331-7019
PURE UUID: d174ef5c-a938-4608-bec6-5ddd426cc8db
ORCID for Nicola Courtier: ORCID iD orcid.org/0000-0002-5714-1096

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Date deposited: 06 Aug 2020 16:36
Last modified: 27 Apr 2022 12:40

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Author: Nicola Courtier ORCID iD

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