title: Ligand-Stabilized Reduced-Dimensionality Perovskites.
abstract: Metal halide perovskites have rapidly advanced thin-film photovoltaic performance; as a result, the materials' observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions. These drive an increased formation energy and should therefore improve material stability. Here we report reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieve the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity.
authors: Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.|Department of Chemistry and Nano Science, Ewha Womans University , 52, Ewhayeodae-gil, Seodaemun-gu, Seoul 03760, Korea.
authors: Li Na
authors: LN
authors: Quan
authors: Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
authors: Mingjian
authors: M
authors: Yuan
authors: Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
authors: Riccardo
authors: R
authors: Comin
authors: Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
authors: Oleksandr
authors: O
authors: Voznyy
authors: Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
authors: Eric M
authors: EM
authors: Beauregard
authors: Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
authors: Sjoerd
authors: S
authors: Hoogland
authors: Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
authors: Andrei
authors: A
authors: Buin
authors: King Abdullah University of Science and Technology (KAUST) , Solar and Photovoltaic Engineering Research Center, and Physical Sciences and Engineering Division, Thuwal 23955-6900, Saudi Arabia.
authors: Ahmad R
authors: AR
authors: Kirmani
authors: King Abdullah University of Science and Technology (KAUST) , Solar and Photovoltaic Engineering Research Center, and Physical Sciences and Engineering Division, Thuwal 23955-6900, Saudi Arabia.
authors: Kui
authors: K
authors: Zhao
authors: King Abdullah University of Science and Technology (KAUST) , Solar and Photovoltaic Engineering Research Center, and Physical Sciences and Engineering Division, Thuwal 23955-6900, Saudi Arabia.
authors: Aram
authors: A
authors: Amassian
authors: Department of Chemistry and Nano Science, Ewha Womans University , 52, Ewhayeodae-gil, Seodaemun-gu, Seoul 03760, Korea.
authors: Dong Ha
authors: DH
authors: Kim
authors: Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
authors: Edward H
authors: EH
authors: Sargent