A new discovery of double phase coexistence inside the perovskite solar cells
Satoshi Uchida a, Tae Woong Kim a, Ludmila Cojocaru b, Takashi Kondo a, Hiroshi Segawa a
a University of Tokyo, Japan, Japan
b Albert-Ludwigs-Universität Freiburg, Albertstraße 21, Freiburg, 79104, Germany
NIPHO
Proceedings of International Conference on Perovskite Thin Film Photovoltaics, Photonics and Optoelectronics (ABXPV18PEROPTO)
Perovskite Thin Film Photovoltaics (ABXPV18). 27-28 Feb
Rennes, France, 2018 February 27th - March 1st
Organizer: Jacky Even
Oral, Satoshi Uchida, presentation 018
DOI: https://doi.org/10.29363/nanoge.abxpvperopto.2018.018
Publication date: 11th December 2017

Recently, organometal halide perovskite solar cells (PSCs) have received great attention. The power conversion efficiency (PCE) of PSCs have shown a dramatic increase and certified PCEs adopting mixed organic cations and halide anions have reached up to 22%. The PCE is considerably affected by photovoltaic property of each component of a PSC. Particularly, because crystal quality of materials is strongly concerned with the electronic properties such as carrier transport, investigation of detailed crystallographic information of the perovskite light absorber is essential. In spite of the significance in the crystallographic information, however, microstructural observation for crystal structure analysis of the perovskite layer has not been actively conducted. In this talk, we will report a microstructural observation about phase coexistence in the perovskite light absorber through transmission electron microscope (TEM) observation.

To obtain the crystallographic information of the perovskite light absorber, a pure methylammonium lead iodide (MAPbI3) layer was formed through spin-coating method assisted by antisolvent in a planar type PSC (Au/Spiro-MeOTAD/ MAPbI3/TiO2/FTO/Glass). MAPbI3 precursor solution used is 1.4 M and the spin-coated MAPbI3 film was annealed at 100˚C for 30 min.

Surprisingly, during the high resolution (HR) TEM observation, we found coexistence of both tetragonal and cubic  structures in the same perovskite layer at room temperature. This new observation is expected to be an important clue of the enhancement of perovskite crystal quality for highly efficient PSCs.

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