Surface Reconstruction of Lead-Free Perovskite Cs2Ag0.6Na0.4InCl6:Bi by Hydroxylation with Blue-Light-Excited Performance.

Molecular surface reconfiguration strategies have been instrumental to performance improvements of halide perovskite photovoltaic applications in recent years. However, research into the optical properties of the lead-free double perovskite Cs2AgInCl6 on the complex reconstructed surface is still lacking. Here, blue-light excitation in double perovskite Cs2Na0.4Ag0.6InCl6 with Bi doping has been successfully achieved by excess KBr coating and ethanol-driven structural reconstruction. Ethanol drives the formation of hydroxylated Cs2-yKyAg0.6Na0.4In0.8Bi0.2Cl6-yBry in the Cs2Ag0.6Na0.4In0.8Bi0.2Cl6@xKBr interface layer. The hydroxyl group adsorbed on the interstitial sites of the double perovskite structure induces a transfer of local space electrons to the [AgCl6] and [InCl6] octahedral regions, enabling them to be excited with blue light (467 nm). The passivation of KBr shell reduces the non-radiative transition probability of excitons. Blue-light-excited flexible photoluminescence devices based on hydroxylated Cs2Ag0.6Na0.4In0.8Bi0.2Cl6@16KBr are fabricated. The application of hydroxylated Cs2Ag0.6Na0.4In0.8Bi0.2Cl6@16KBr as down-shift layer in GaAs photovoltaic cell module can increase its power conversion efficiency by 3.34%. The surface reconstruction strategy provides a new way to optimize the performance of lead-free double perovskite.

Efficient Removal of Perfluorinated Chemicals from Contaminated Water Sources Using Magnetic Fluorinated Polymer Sorbents.

Efficient removal of per- and polyfluoroalkyl substances (PFAS) from contaminated waters is urgently needed to safeguard public and environmental health. In this work, novel magnetic fluorinated polymer sorbents were designed to allow efficient capture of PFAS and fast magnetic recovery of the sorbed material. The new sorbent has superior PFAS removal efficiency compared with the commercially available activated carbon and ion-exchange resins. The removal of the ammonium salt of hexafluoropropylene oxide dimer acid (GenX) reaches >99 % within 30 s, and the estimated sorption capacity was 219 mg g-1 based on the Langmuir model. Robust and efficient regeneration of the magnetic polymer sorbent was confirmed by the repeated sorption and desorption of GenX over four cycles. The sorption of multiple PFAS in two real contaminated water matrices at an environmentally relevant concentration (1 ppb) shows >95 % removal for the majority of PFAS tested in this study.

Mid-Infrared Luminescence of the High Stability Perovskite CsPb1-xErxBr3-ZrF4-BaF2-LaF3-AlF3-NaF Fluoride Glass.

Perovskites have been studied because of their adjustable wavelength range, high color purity, and wide color gamut. However, they still face some problems such as poor stability and insufficient infrared luminescence. The perovskite glass can improve the stability and luminescence properties of the perovskite. In this paper, a highly stable CsPb1-xErxBr3-ZBLAN fluoride glass with mid-infrared and visible light emission was prepared. The ZBLAN fluoride glass has good inertness, which can improve the stability of the CsPb1-xErxBr3 perovskite. The CsPb1-xErxBr3-ZBLAN fluoride glass can prevent the perovskite from being destroyed by water, oxygen, and laser. The Er3+ replaces Pb2+ to bond with Br- to become the luminescent center of the CsPb1-xErxBr3-ZBLAN perovskite glass, which extends the luminescence to the mid-infrared region. In addition, its luminescent intensity is significantly higher than those of the ZBLAN-Er glass and CsPb1-xErxBr3 perovskite. After irradiation with a 365 nm UV lamp for 13 h, the luminescence intensity of the CsPb1-xErxBr3-ZBLAN perovskite glass decreases only by 10%. The EDS spectrum shows that the elements of the CsPb1-xErxBr3 perovskite are uniformly distributed in the glass matrix. The X-ray diffraction spectrum shows that the sample has both the CsPb1-xErxBr3 perovskite phase and the glass phase. This indicates that CsPb1-xErxBr3 is well crystallized in the ZBLAN glass matrix. The three parameters calculated by the Judd-Ofelt theory show that the CsPb1-xErxBr3 perovskite can increase the covalency and asymmetry around the rare earth ion Er3+. The transmission electron microscope can clearly see the morphological structure of the CsPb1-xErxBr3 perovskite in the ZBLAN glass matrix. The infrared Fourier transform spectroscopy shows that the sample has lower phonon energy. This proves that the sample has good infrared luminescence characteristics. Finally, the visible and infrared light sources were prepared. Under the irradiation of the 365 nm ultraviolet lamp and 980 nm laser, the perovskite glass produces green light and infrared emission.

Novel cryogenic dual-emission mechanism of lead-free double perovskite Cs2AgInCl6 and using SiO2 to enhance their photoluminescence and photostability.

Lead halide perovskite have attracted world-wide attention regarding their serious hazards on ecological environment and human health. To improve both the emission intensity and stability of Cs2AgInCl6, this study explores using SiO2 to structurally adjust Cs2AgInCl6. Note that including SiO2 changed the growth style and crystal morphology of Cs2AgInCl6 from an octahedron to a truncated octahedron. After structural adjustment, the unit cells scattered, and the absorption limit broke. Moreover, SiO2 was demonstrated to passivate the material's surface to form an anti-oxidation protective layer. Consequently, the photoluminescence emission intensity increased by 181.5% and the stability of Cs2AgInCl6 improved by 83.11%. This work provides a methodology and reference for future improvements to the luminescence of Cs2AgInCl6. Furthermore, a novel double-emission phenomenon (λex = 365 nm: λem ≈ 580 nm; λex = 325 nm: λem ≈ 505 nm) of Cs2AgInCl6 at cryogenic temperatures (20 K) was discovered; this phenomenon explains the shoulder emission problem of 400-450 nm at room temperature and clarifies the luminescence mechanism of Cs2AgInCl6.

Epitaxial growth of highly stable perovskite CsPbBr3/nZnS/Al core/multi-shell quantum dots with aluminium self-passivation.

As a new type of colloidal nanocrystals, perovskite quantum dots (QDs) have received widespread attention. Water and oxygen in the air can affect the luminous efficiency of quantum dots, which can degrade the surface of QDs and affect their luminescence efficiency. Herein we discuss the synthesis of high-quality QDs using an uncomplicated coating method by which an ultrathin epitaxial Al self-passivation layer bearing homogeneous ligands can be coated on the QDs. The core/shell perovskite QDs maintain high luminescence efficiency and photostability. The CsPbBr3/2ZnS/Al QDs were only attenuated by 10% after 14 h of exposure to LED light. The temperature-dependent photoluminescence properties of the all-inorganic perovskite QDs, such as the PL intensity, emission peak position, and the full width at half maximum (FWHM), were investigated. The results indicated that the activation energy of QDs increases with the increase of the number of ZnS shell layers, its stability increases significantly. The introduction of Al does not change the luminescence mechanism of QDs. Finally, we have made flexible light-emitting device with CsPbBr3/2ZnS/Al QDs.

Stable Luminescence of CsPbBr3/nCdS Core/Shell Perovskite Quantum Dots with Al Self-Passivation Layer Modification.

Perovskite quantum dots (PQDs) are among the most important luminescent semiconducting materials; however, they are unstable. Exposure to light, heat, and air can lead to irreversible degradation, which results in fluorescence quenching. Therefore, defects in PQDs significantly limit their practical application. Herein, we describe a simple method to enhance the photostability of CsPbBr3/nCdS QDs, which involves doping their shells with aluminum. The temperature-dependent photoluminescence (PL) of colloidal CsPbBr3/nCdS/Al2O3 QDs is investigated, and the thermal quenching of PL, blue shift of the optical band gap, and PL line width broadening are observed in each QD sample. Al2O3 layers on the CsPbBr3/nCdS QDs can effectively prevent photodegradation. Nonlinear, temperature-dependent exciton-phonon coupling and lattice dilation leads to radiative and nonradiative relaxation processes at temperatures ranging from 10 to 300 K; moreover, changes in the band gap and PL spectral line broadening are observed.