The Effect of Moisture in the Formation of CH3NH3PbI3 Perovskite
Laura Herz a, Jay Patel a, Rebecca Milot a, Adam Wright a, Michael Johnston a
a Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV16)
Swansea, United Kingdom, 2016 June 29th - July 1st
Organizers: James Durrant, Henry Snaith and David Worsley
Poster, Jay Patel, 334
Publication date: 28th March 2016

The Effect of Moisture in the Formation of CH3NH3PbI3 Perovskite

It is thus far ambiguous why inorganic-organic perovskite devices have different device performance when processed in a humid environment or not. With the use of Fourier transform infrared spectroscopy (FTIR) we are able to attribute the effect of moisture, on the different aspects of the formation and growth of perovskite crystallites.

Using an altered two step thermal evaporation method we prevent the rapid diffusion of the inorganic and organic layers, thus allowing us to observe the chemical transformations that occur in the initial stages of inorganic-organic perovskite crystal formation.[1,2] Using  techniques such as visible light transmission,[3] X-ray diffraction and photoluminescence lifetime measurements, we correlate the findings with the chemical changes that were observed. Furthermore using these techniques, we observe dynamic processes that lead to the growth of perovskite crystallites as they are exposed to moisture.

It was found that the CH3NH3I (MAI) diffuses into the PbI2 lattice to form CH3NH3PbI3 (MAPbI3). In vacuum, the transformation to MAPbI3 is incomplete as there are local areas of unreacted MAI retained in the film. However, exposure to moisture allows for conversion of the unreacted MAI to MAPbI3, demonstrating that moisture is essential in making MAI more mobile, hence aiding initial perovskite crystallization and thereafter the growth of crystal domains.[4]

[1]         S. D. Stranks, S. M. Wood, K. Wojciechowski, F. Deschler, M. Saliba, H. Khandelwal, J. B. Patel, S. J. Elston, L. M. Herz, M. B. Johnston, A. P. H. J. Schenning, M. G. Debije, M. K. Riede, S. M. Morris, H. J. Snaith, Nano Lett. 2015, 15, 4935.

[2]         M. Saliba, S. M. Wood, J. B. Patel, P. K. Nayak, J. Huang, J. A. Alexander-Webber, B. Wenger, S. D. Stranks, M. T. Hörantner, J. T.-W. Wang, R. J. Nicholas, L. M. Herz, M. B. Johnston, S. M. Morris, H. J. Snaith, M. K. Riede, Adv. Mater. 2016, 28, 923.

[3]         M. A. Pérez-Osorio, R. L. Milot, M. R. Filip, J. B. Patel, L. M. Herz, M. B. Johnston, F. Giustino, J. Phys. Chem. C 2015, 119, 25703.

[4]        J. B. Patel, R. L. Milot, A. D. Wright, L. M. Herz, M. B. Johnston, J. Phys. Chem. Lett. 2016, 7, 96.



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