Deciphering Perovskite Decomposition in a humid atmosphere with TOF-GISANS
Adam Urwick a, Gabriel Perez b, Francesco Bastianin c, Alan Dunbar d
a Department of chemical and biological engineering, University of Sheffield, Sheffield S10 2TN, Reino Unido, United Kingdom
b ISIS Neutron and Muon Source Science and Technology Facilities Council, Rutherford Appleton Laboratory Harwell Campus, Didcot
c SmartKem ltd. Hexagon Tower, Delaunays Rd, Blackley, Manchester M9 8GQ
d University of Sheffield, Hounsfield Road, United Kingdom
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, Adam Urwick, 295
Publication date: 20th April 2022

Alloying the A-site of ABX3 perovskites is a successful technique of improving moisture stability of perovskite films for optoelectronic applications. Despite improvements these films still undergo moisture induced degradation reducing device lifetime and performance.

Time-of-flight Grazing Incidence Small Angle Neutron Scattering (TOF-GISANS) is capable of identifying low atomic weight phases during degradation and offering depth resolution.

We use TOF-GISANS to investigate moisture induced degradation pathways in mixed perovskite systems fabricated under ambient conditions and then exposed to 90% rH in the dark for up to 12 hrs, showing poor stoichiometric homogeneity and facile formation of deuterated by-products.

We find evidence indicative of formation of PbI2 and PbBr2 in the surface of MAPbI3, FA0.83MA0.17Pb(I0.83Br0.17)3, and FA0.83Cs0.17Pb(I0.83Br0.17)3 films, with degradation reduced in films containing Cs. Cs0.05(FA0.83MA0.17)0.95Pb(I0.84Br0.16)3 shows impressive phase resilience, with minimal segregation to other phases, though still exhibiting morphological degradation. Moisture induced degradation results in decreasing average particle size as perovskite grains swell and fragment from the grain periphery inwards. 

TOF-GISANS is demonstrated as a powerful tool for characterisation of these materials, with significant potential for future investigations into phase changes in thin films.


Experiments at the ISIS Pulsed Neutron and Muon Source were supported by a beamtime allocation from the Science and Technology Facilities Council. We also gratefully acknowledge Sarah Rodgers for her assistance on the Sans2d Time-of-flight Small-Angle Neutron Scattering instrument.

This work benefited from the use of the SasView application, originally developed under NSF award DMR-0520547. SasView contains code developed with funding from the European Union’s Horizon 2020 research and innovation programme under the SINE2020 project, grant agreement No 654000. See other publications and documentation concerning SasView at

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