Understanding texture formation in methylammonium lead iodide perovskites
Joel A. Smith a, Onkar Game a, Natalia Martsinovich b, Adam Shnier c, Rachel Kilbride a, Mary O'Kane a, Daniel Wamwangi d, David S. Billing c, Andrew J. Parnell a, David G. Lidzey a
a Department of Physics and Astronomy, University of Sheffield, UK
b Department of Chemistry, University of Sheffield, Sheffield, Sheffield, S3 7HF
c University of the Witwatersrand, South Africa, Jan Smuts Avenue, 1, Johannesburg, South Africa
d University of the Witwatersrand, South Africa, Jan Smuts Avenue, 1, Johannesburg, South Africa
nanoGe Fall Meeting
Proceedings of nanoGe Fall Meeting19 (NGFM19)
#PERInt19. Interplay of composition, structure and electronic properties in halide-perovskites
Berlin, Germany, 2019 November 3rd - 8th
Organizer: Pablo P. Boix
Poster, Joel A. Smith, 437
Publication date: 18th July 2019

Hybrid organic-inorganic perovskite solar cells have generated huge research interest for their highly desirable photovoltaic performance (over 25% certified PCE1), with high quality semiconducting materials formed at low temperature and from solution. Methylammonium (CH3NH3+) lead iodide (MAPbI3), can be crystallographically oriented, and may have enhanced carrier transport between charge selective interfaces,2 with various strategies employed to induce this orientation,3 or texture. However, the detailed understanding of the evolution of crystallographic orientation in MAPbI3 is still poorly understood.

In situ grazing incidence wide-angle X-ray scattering (GIWAXS) from synchrotron radiation allows for process monitoring of rapid crystallization processes in solution processed films.5 Here we use in situ GIWAXS to understand the evolution of texture in methylammonium lead iodide thin films in different temperatures and environments.  We show that rather than directly proceeding to crystalline phase (MAPbI3) as previously thought, the intermediates that form during processing drive the crystallization of the perovskite films. These precursor intermediates show temperature dependency, and have strong orientation, which consequently influence the conversion into oriented MAPbI3. The resulting films exhibit more complex non-uniaxial grain orientation than presently thought, progressing current understanding of structure formation and highlighting the importance of two-dimensional scattering data in analyzing such material systems.

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