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Interpretation of inverted photocurrent transients in organic lead halide perovskite solar cells; proof of the field screening by mobile ions and determination of the space charge layer widths

Title: Interpretation of inverted photocurrent transients in organic lead halide perovskite solar cells; proof of the field screening by mobile ions and determination of the space charge layer widths
Authors: Belisle, RA
Nguyen, WH
Bowring, AR
Calado, P
Li, X
McGehee, MD
Barnes, PRF
O'Regan, BC
Item Type: Journal Article
Abstract: In Methyl Ammonium Lead Iodide (MAPI) perovskite solar cells, screening of the built in field by mobile ions has been proposed as part of the cause of the large hysteresis observed in the current/voltage scans in many cells. We show that photocurrent transients measured immediately (e.g. 100 μs) after a voltage step can provide direct evidence that this field screening exists. Just after a step to forward bias, the photocurrent transients are reversed in sign (i.e. inverted), and the magnitude of the inverted transients can be used to find an upper bound on the width of the space charge layers adjacent to the electrodes. This in turn provides a lower bound on the mobile charge concentration, which we find to be 1 x 10 17 /cm 3 . Using a new photocurrent transient experiment, we show that the space charge layer thickness remains approximately constant as a function of bias, as expected for mobile ions in a solid electrolyte. We also discuss additional characteristics of the inverted photocurrent transients that imply either an unusually stable deep trapping, or a photo effect on the mobile ion conductivity.
Issue Date: 21-Dec-2016
Date of Acceptance: 13-Dec-2016
URI: http://hdl.handle.net/10044/1/50779
DOI: https://dx.doi.org/10.1039/C6EE02914K
ISSN: 1754-5706
Publisher: Royal Society of Chemistry
Start Page: 192
End Page: 204
Journal / Book Title: Energy & Environmental Science
Volume: 10
Copyright Statement: This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Sponsor/Funder: Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (E
Engineering & Physical Science Research Council (E
Funder's Grant Number: EP/J002305/1
EP/H040218/1
n/a
Keywords: Science & Technology
Physical Sciences
Technology
Life Sciences & Biomedicine
Chemistry, Multidisciplinary
Energy & Fuels
Engineering, Chemical
Environmental Sciences
Chemistry
Engineering
Environmental Sciences & Ecology
ORGANOMETAL TRIHALIDE PEROVSKITE
ANOMALOUS HYSTERESIS
THIN-FILMS
EFFICIENT
MIGRATION
BEHAVIOR
MD Multidisciplinary
Energy
Publication Status: Published
Appears in Collections:Physics
Chemistry
Experimental Solid State
Faculty of Natural Sciences