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Issue 45, 2016
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Cs+ incorporation into CH3NH3PbI3 perovskite: substitution limit and stability enhancement

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Abstract

In this study we systematically explored the mixed cation perovskite Csx(CH3NH3)1−xPbI3. We exchanged the A-site cation by dipping MAPbI3 films into a CsI solution, thereby incrementally replacing the MA+ in a time-resolved dipping process and analysed the resulting thin-films with UV-Vis, XRD, EDAX, SEM and optical depth-analysis in a high-throughput fashion. Additional in situ UV-Vis and time-resolved XRD measurements allowed us to look at the kinetics of the formation process. The results showed a discontinuity during the conversion. Firstly, small amounts of Cs+ are incorporated into the structure. After a few minutes, the Cs content approaches a limit and grains of δ-CsPbI3 occur, indicating a substitution limit. We compared this cation exchange to a one-step crystallisation approach and found the same effect of phase segregation, which shows that the substitution limit is an intrinsic feature rather than a kinetic effect. Optical and structural properties changed continuously for small Cs incorporations. Larger amounts of Cs result in phase segregation. We estimate the substitution limit of CsxMA1−xPbI3 to start at a Cs ratio x = 0.13, based on combined measurements of EDAX, UV-Vis and XRD. The photovoltaic performance of the mixed cation perovskite shows a large increase in device stability from days to weeks. The initial efficiency of mixed CsxMA1−xPbI3 devices decreases slightly, which is compensated by stability after a few days.

Graphical abstract: Cs+ incorporation into CH3NH3PbI3 perovskite: substitution limit and stability enhancement

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Publication details

The article was received on 12 Jul 2016, accepted on 26 Oct 2016 and first published on 26 Oct 2016


Article type: Paper
DOI: 10.1039/C6TA05869H
Citation: J. Mater. Chem. A, 2016,4, 17819-17827
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    Cs+ incorporation into CH3NH3PbI3 perovskite: substitution limit and stability enhancement

    R. G. Niemann, L. Gouda, J. Hu, S. Tirosh, R. Gottesman, P. J. Cameron and A. Zaban, J. Mater. Chem. A, 2016, 4, 17819
    DOI: 10.1039/C6TA05869H

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