Role of fluoride and fluorocarbons in enhanced stability and performance of halide perovskites for photovoltaics

Stability Improvement of 2D Perovskite by Fluorinated‐Insulator

“…[45][46][47] However, researches about stabilizing optical properties by directly utilizing fluorinated organic-ligand as a 2D-HOIP insulating layer are rare. [48,49] In this work, in order to enhance the stabilities of 2D-HOIP, fluorinated cation (2-(4-fluorophenyl) ethylamine [F-PEA]) was chosen as the organic ligand to replace the phenyl ethylamine (PEA) in (PEA) 2 PbI 4 (PEPI), as the schematic diagram shown In this study, the interface of 2D hybrid organic-inorganic perovskites L 2 PbI 4 (here L stands for phenylethylamine, PEA) is engineered by fluorine substitution in its organic insulator layers, and the stability of the perovskite is investigated. For the water-resistance, the fluorinated-perovskite maintained 90% photoluminescence intensity of its initial state after 800-h exposure to relative humidity 75-80%, while it is 47% for that without fluorine, resulting from hydrophobic property of fluorinated insulator.…”

Design Principles of Large Cation Incorporation in Halide Perovskites

“…On the other hand, the partial substitution of MA with a larger cation at different concentrations brings several advantages for the stability and efficiency of the devices [ 34 , 47 ] while preserving the 3D connectivity of the octahedral network [ 46 ]. For example, the large dipole moment of molecular cation in mixed-cation halide perovskites [ 46 ] is a desired property that is known to enhance the charge carrier separation when the incident light generates photoexcited electron-hole pairs.…”

“…Interestingly, due to the high electronegativity of fluorine, fluorinated cations can introduce strong ionic and intermolecular bonding within the perovskite material. They are also helpful for passivating surfaces, thereby suppressing their chemical reactivity in the presence of moisture or contact with water [ 34 ]. The lattice distortions induced by fluorinated cations, which are usually even larger than MA, result in a broad and robust photoluminescence spectrum upon excitations of samples with light sources at frequencies below the bandgap [ 35 ].…”

“…Fluorinated organic cation’s partial or total substitution is increasingly being reported as an efficient way to tune the properties of the perovskite and enhance their stability [ 34 , 37 ] by strengthening some of the weak hydrogen bonds between the organic cations and the surrounding [PbI 3 ] framework [ 36 ].…”

Nanometer-Thick Cs2SnI6 Perovskite–Polyethylene Glycol Dimethacrylate Composite Films for Highly Stable Broad-Band Photodetectors

“…However, a two-step phase change occurs from CsSnI 3 to Cs 2 SnI 6 and takes at least 3–5 days. Another method, called a solution-based technique in which metal halide precursors are dissolved in polar organic solvents with high boiling points like dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), often produces impurities (SnO 2 ) and poor-quality films. , Synthesis of Cs 2 SnI 6 , which is realized using different precursors like cesium acetate and tin acetate in a HI mixture, and its film deposition by drop-casting have also been reported . The above methods clearly provide a roadmap for the production of Cs 2 SnI 6 that guarantees long-term stability.…”