Halide Perovskites

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Entre pérovskites 2D et 3D : le d-MAPI

Our study of temperature dependent micro-photoluminescence which shows a strong spatial inhomogeneity related to the presence of microcrystalline grains, which can be both bright and dark. In all of the tri-iodide based materials there is evidence that the tetragonal to orthorhombic phase transition observed around 160 K does not occur uniformly across the sample with domain formation related to the underlying microcrystallite grains, some of which remain in the high temperature, tetragonal, phase even at very low temperatures. At low temperature the tetragonal domains can be significantly influenced by local defects in the layers or the introduction of residual levels of chlorine in mixed halide layers or dopant atoms such as aluminium.

Publication :
Spatially resolved studies of the phases and morphology of methylammonium and formamidinium lead tri-halide perovskites
K. Galkowski, A. A. Mitioglu, A. Surrente, Z. Yang, D. K. Maude, P. Kossacki, G. E. Eperon, J. T.-W. Wang,H. J. Snaith, P. Plochocka, R. J. Nicholas
Nanoscale 2017, 9, 3222

Abstract
3D and 2D hybrid perovskites which are known for more than 20 years have emerged recently as promising materials for optoelectronic applications, particularly the 3D compound (CH3NH3)PbI3 (MAPI). Here, we report on the discovery of a new family of hybrid perovskites called d-MAPI : the association of PbI2 with both methyl ammonium (MA+) and hydroxyethyl ammonium (HEA+) cations leads to a series of five compounds whose general formulation is (MA)1-2.48x(HEA)3.48x[Pb1-xI3-x]. These materials which are lead and iodide deficient compared to MAPI, while keeping the 3D architecture, can be considered as a bridge between the 2D and 3D materials. Moreover, they can be prepared as crystallized thin films by spin-coating. These new 3D materials appear very promising for optoelectronic applications, not only because of their reduced lead content, but also in account of the large flexibility of their chemical composition through potential substitutions of MA+, HEA+, Pb2+ and I- ions.