Halide Perovskite Microstrain: Are We Measuring Correctly?

Susana Iglesias-Porras^a, Dumitru Sirbu^b, Noel Healy^b, Pablo Docampo^c, Elizabeth Gibson^a

^aSchool of Natural and Environmental Sciences, Newcastle University, UK, Newcastle upon Tyne, Reino Unido, Newcastle upon Tyne, United Kingdom

^bSchool of Mathematics, Statistics and Physics, Newcastle University, Herschel Building, NE1 7RU, Newcastle upon Tyne, UK.

^cSchool of Chemistry, University of Glasgow, University Pl, G12 8QQ, Glasgow, UK

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)

València, Spain, 2022 May 19th - 25th

Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson

Poster, Susana Iglesias-Porras, 219
Publication date: 20th April 2022

Partial element substitutions in halide perovskites have been implemented over the years to improve the quality of the devices: from boosting their optoelectronic properties to increasing their stability. [1-5] However, incorporating elements of different atomic sizes can alter the lattice microstrain. Variations in this parameter have often been associated with both beneficial and detrimental changes in the perovskite optoelectronic properties and phase stability, [2-10] yet other studies affirm their impact to be of minor relevance.[11] Controversy on these results triggers a preceding question: can we trust the reliability of the state-of-the-art methods used in the calculation of halide perovskite microstrain? To solve this conundrum, in this work, we analysed the validity of the halide perovskite XRD microstrain results reported both in the literature and in the lab using integral breadth methods. We highlight the recurring presence of a significant error at low 2θ angles: parallel planes displaying different values of microstrain; a clear breach of the constraint imposed by the Wilson-Stokes approximation. We explored the origins of this disparity by first minimizing the instrumental errors associated with the diffractometer configuration and then optimizing the fit of the instrumental curve using several reference materials. Despite successful instrumental error minimization, we found the parallel plane decreasing microstrain trend in MAPbI₃, MAPbBr₃ and CsFAMAPb(IBr)₃ perovskite thin films to remain, suggesting the presence of a hitherto unreported microstrain gradient across the order-of-diffraction.

References:

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Acknowledgements:

Nathan Hill at Newcastle University for the crystallization of the (PEA)₂PbI₄ single crystal.

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