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Hybrid perovskite solar cells have been capturing an enormous research interest in the energy sector due to their extraordinary performances and ease of fabrication. However, low device lifetime, mainly due to material and device degradation upon water exposure, challenges their near-future commercialization. Here, we synthesized a new fluorous organic cation used as organic spacer to form a low-dimensional perovskite (LDP) with an enhanced water-resistant character. The LDP is integrated with three-dimensional (3D) perovskite absorbers in the form of MAFAPbI (FA = NHCH = NH, MA = CHNH) and CsFAMAPbIBr In both cases, a LDP layer self-assembles as a thin capping layer on the top of the 3D bulk, making the perovskite surface hydrophobic. Our easy and robust approach, validated for different perovskite compositions, limits the interface deterioration in perovskite solar cells yielding to >20% power conversion efficient solar cells with improved stability, especially pronounced in the first hours of functioning under environmental conditions. As a consequence, single and multijunction perovskite devices, such as tandem solar cells, can benefit from the use of the waterproof stabilization here demonstrated, a concept which can be further expanded in the perovskite optoelectronic industry beyond photovoltaics.

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Four different fluorene–dithiophene derivative-based hole-transporting materials (HTMs) (SO7–10) have been synthesized via a facile route and were successfully used in the fabrication of formamidinium lead bromide perovskite solar cells. Detailed characterization of the new compounds was carried out through 1H/13C NMR spectroscopy, mass spectrometry, ultraviolet–visible and photoluminescence spectroscopy, and cyclic voltammetry. Under AM1.5 G illumination, the mesoscopic CH­(NH2)2PbBr3 perovskite solar cell employing SO7 as the HTM displayed an outstanding photovoltage (V oc) of 1.5 V with an efficiency (η) of 7.1%. The photovoltaic performance is on par with the device using the state-of-the-art Spiro-OMeTAD as HTM, which delivered a V oc of 1.47 V and a maximum η of 6.9%. A density functional theory approach with GW simulations including spin–orbit coupling and electrochemical measurements revealed deeper highest occupied molecular orbital levels for newly synthesized fluorene–dithiophene derivatives, which eventually makes them promising HTMs for perovskite solar cells, especially when high photovoltage is desired.

Two dimensional (2D) organic-inorganic hybrid perovskites have recently attracted enormous attention due to their higher environmental stability with respect to three-dimensional (3D) perovskites and larger structural tunability. The layered structure relaxes constraints on the dimensions of the organic cations that alternate the inorganic sheets, opening up a large choice on the organics, ultimately enabling the creation of tunable layered perovskites. Here, we report on a series of fluorous cations, varying in size and shape, as building blocks for a new family of fluorous 2D lead-iodide perovskites. These display a large tunability in the optical and dielectric properties depending on the structure of the fluorous cations. Importantly, despite the invariant inorganic framework, the 2D perovskite electronic structure is strongly affected by the cation size. The longer the cation, the smaller the 2D perovskite band gap and the exciton binding energy (reducing from 400 meV down to 130 meV). Such variation is induced by the strain in the inorganic sheet, resulting in a more dispersed valence and conduction bands, in turn yielding a smaller band gap. In addition, a smaller effective mass for the 2D perovskite with the longest cation is calculated, for which improved transport properties are anticipated. Importantly, the fluorous moiety confers extreme stability to the 2D perovskite and enhanced the hydrophobic character of the perovskite surface, which remains perfectly stable for more than one month in ambient conditions.

Keywords: Biaryls / Biphasic catalysis / Epoxidations / Fluorinated ligands / ManganeseThe synthesis of sterically hindered chiral (salen)manganese complexes bearing perfluoroalkyl ponytails and their use in asymmetric epoxidation reactions are described. For better understanding of the relative influences of steric and electronic effects on the enantioselectivity of the fluorous catalysts, the epoxidation of 1,2-dihydronaphthalene and benzosuberene was first studied under homogeneous conditions. It was shown that the presence of sterically demanding tertbutyl groups and, to a lesser degree, the displacement of the electron-withdrawing perfluoroalkyl substituents from the ligand core provide ees higher than those attainable with first generation fluorous chiral (salen)manganese complexes featuring perfluoroalkyl substituents in the key positions (3,3Ј

[structure: see text] Poly(ethylene glycol)-supported TEMPO (PEG-TEMPO) has been prepared, and its catalytic activity in the chemoselective oxidation of alcohols with stoichiometric amounts of organic or inorganic oxidants has been investigated. The new metal-free catalyst exhibits high activity and is easily removed from the reaction mixture by filtration. Recycling experiments showed that PEG-TEMPO can be reused up to six times with no loss of catalytic activity.

[reaction: see text] A new poly(ethylene glycol)-supported porphyrin has been prepared and its ability as a promoter in photooxidation reactions has been studied. The PEG-supported catalyst exhibits high activity, comparable to that of a nonanchored sensitizer, and it is easily removable by filtration from the reaction mixture. The polymer-bound porphyrin has been recycled up to six times with no loss of chemical and stereochemical efficiency.