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
Open Access
- 21 December 2016
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Energy & Environmental Science
- Vol. 10 (1), 192-204
- https://doi.org/10.1039/c6ee02914k
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 × 1017 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.Funding Information
- Office of Energy Efficiency and Renewable Energy (DEEE0006707)
- Engineering and Physical Sciences Research Council (EP/G037515/1, EP/I019278/1, EP/J002305/1, EP/M014797/1, EP/M023532/1, EP/M025020/1)
This publication has 44 references indexed in Scilit:
- Evidence for ion migration in hybrid perovskite solar cells with minimal hysteresisNature Communications, 2016
- A vacuum flash-assisted solution process for high-efficiency large-area perovskite solar cellsScience, 2016
- Ionic transport in hybrid lead iodide perovskite solar cellsNature Communications, 2015
- High-performance photovoltaic perovskite layers fabricated through intramolecular exchangeScience, 2015
- The dynamics of methylammonium ions in hybrid organic–inorganic perovskite solar cellsNature Communications, 2015
- Extremely Slow Photoconductivity Response of CH3NH3PbI3 Perovskites Suggesting Structural Changes under Working ConditionsThe Journal of Physical Chemistry Letters, 2014
- Anomalous Hysteresis in Perovskite Solar CellsThe Journal of Physical Chemistry Letters, 2014
- Unusual defect physics in CH3NH3PbI3 perovskite solar cell absorberApplied Physics Letters, 2014
- 6.5% efficient perovskite quantum-dot-sensitized solar cellNanoscale, 2011
- Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic CellsJournal of the American Chemical Society, 2009