Hydration stability of hybrid organic-inorganic halide perovskite powders, single crystals and thin-films by gravimetric water vapour sorption analysis
Anthony Houghton a, Daryl Williams a
a Department of Chemical Engineering, Imperial College London, United Kingdom
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Poster, Anthony Houghton, 244
Publication date: 11th February 2019

Hybrid organic-inorganic lead halide perovskites have undoubtably become a material of high research interest in the last decade since it was realised that they could work as a visible-light sensitizer in 2009 [1]. Furthermore, applications of interest that are rapidly growing in recent years include light-emitting diodes and photodetectors [2]. The power conversion efficiency of perovskite based solar cells has now reached over 23% [3], which is around that of photovoltaic technology such as CdTe and CIGS thin-films. However, the environmental stability of perovskites can be problematic and is limiting their potential as a viable candidate for commercialisation.

The most researched perovskite, methylammonium lead iodide (MAPI), is known to suffer detrimental effects upon exposure to moisture. Although there have been many studies on the water stability, particularly of its effect on the electronic and optoelectronic properties and device fabrication and performance, the current study focuses on the diffusion and sorption of moisture on the surface and bulk of perovskite materials. These factors will be investigated via Dynamic Vapour Sorption (DVS) water vapour sorption experiments.

DVS is a gravimetric technique that measures the change in mass of a sample when exposed to a continuous flow of a gas or vapour stream at a defined solute partial pressure. Additionally, this can be done at a range of temperatures. From the experimental data, many properties of the material tested can be found including diffusion and sorption kinetics of water, adsorption/desorption isotherms, surface area and guest-molecule induced phase changes. These properties are critical for any material that is planned for commercialisation. Systematic DVS studies are reported here for MAPI powders, single crystals and thin-films, where this pristine perovskite will be compared to mixed or doped perovskites, as well as other more stable forms.

This work was supported by the Doctoral Training Partnership programme from the Engineering and Physical Sciences Research Council in the United Kingdom.

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