T1.5 Uniaxial Expansion of the 2D Ruddlesden-Popper Perovskite Family for Improved Environmental Stability

Ioannis Spanopoulos (Northwestern University), Mercouri Kanatzidis (Northwestern University), Ido Hadar (Northwestern University), Weijun Ke (Northwestern University),
Qing Tu (Northwestern University), Vinayak Dravid (Northwestern University)

The unique hybrid nature of 2D Ruddlesden-Popper (R-P) perovskites has bestowed upon them not only tunability of their electronic properties but also high-performance electronic devices with improved environmental stability as compared to their 3D analogs. However, there is limited information about their inherent heat, light and air stability, and how different parameters such the inorganic layer number and length of organic spacer molecule affect stability. To gain deeper understanding on the matter we have expanded the family of 2D R-P perovskites, by utilizing pentylamine (PA)2(MA)n-1PbnI3n+1 (n = 1-6, PA = CH3(CH2)4NH3+, C5) and hexylamine (HA)2(MA)n-1PbnI3n+1 (n = 1-4, HA = CH3(CH2)5NH3+, C6) as the organic spacer molecules between the inorganic slabs, creating two new series of layered materials in single crystal form, for up to n = 6 and 4 layers, respectively. The increase in the length of the organic spacer molecules does not affect their optical properties, however it has a pronounced effect on the air, heat and light stability of the fabricated thin films. We fabricated films on various substrates, and performed extensive environmental stability tests, evaluating their air, heat and light stability, both with and without encapsulation. Multiparameter, invaluable information was extracted from these studies, which showed that for the same number of layers the PA based materials, exhibited improved heat, light and air stability (e.g. stable for 450 days in air), as compared to BA, HA and 3D analogues. Furthermore, we verified for the first time that hybrid halide perovskites are inherently heat and light stable in the absence of moisture, a most critical finding for their potential commercialization. Lastly, evaluation of the out of plane mechanical properties of the corresponding materials showed that their soft and flexible nature can be compared to the current commercially available polymer substrates (e.g. PMMA), rendering them suitable for fabricating flexible and wearable electronic devices, expanding their utilization beyond photovoltaic applications.

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Ioannis Spanopoulos
Location: Technological Institute LR4