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      Chemical Analysis of the Interface between Hybrid Organic-Inorganic Perovskite and Atomic Layer Deposited Al2O3

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          Abstract

          Ultrathin metal oxides prepared by atomic layer deposition (ALD) have gained utmost attention as moisture and thermal stress barrier layers in perovskite solar cells (PSCs). We have recently shown that 10 cycles of ALD Al2O3 deposited directly on top of the CH3NH3PbI3–x Cl x perovskite material, are effective in delivering a superior PSC performance with 18% efficiency (compared to 15% of the Al2O3-free cell) with a long-term humidity-stability of more than 60 days. Motivated by these results, the present contribution focuses on the chemical modification which the CH3NH3PbI3–x Cl x perovskite undergoes upon growth of ALD Al2O3. Specifically, we combine in situ Infrared (IR) spectroscopy studies during film growth, together with X-ray photoelectron spectroscopy (XPS) analysis of the ALD Al2O3/perovskite interface. The IR-active signature of the NH3 + stretching mode of the perovskite undergoes minimal changes upon exposure to ALD cycles, suggesting no diffusion of ALD precursor and co-reactant (Al(CH3)3 and H2O) into the bulk of the perovskite. However, by analyzing the difference between the IR spectra associated with the Al2O3 coated perovskite and the pristine perovskite, respectively, changes occurring at the surface of perovskite are monitored. The abstraction of either NH3 or CH3NH2 from the perovskite surface is observed as deduced by the development of negative N–H bands associated with its stretching and bending modes. The IR investigations are corroborated by XPS study, confirming the abstraction of CH3NH2 from the perovskite surface, whereas no oxidation of its inorganic framework is observed within the ALD window process investigated in this work. In parallel, the growth of ALD Al2O3 on perovskite is witnessed by the appearance of characteristic IR-active Al–O–Al phonon and (OH)–Al=O stretching modes. Based on the IR and XPS investigations, a plausible growth mechanism of ALD Al2O3 on top of perovskite is presented.

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          23.6%-efficient monolithic perovskite/silicon tandem solar cells with improved stability

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            Low-Temperature Al2O3Atomic Layer Deposition

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                Author and article information

                Journal
                ACS Applied Materials & Interfaces
                ACS Appl. Mater. Interfaces
                American Chemical Society (ACS)
                1944-8244
                1944-8252
                January 09 2019
                January 09 2019
                Article
                10.1021/acsami.8b18307
                04fadb6a-f67d-41ad-a31e-a56640598b1a
                © 2019
                History

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