MA Cation-Induced Diffusional Growth of Low-Bandgap FA-Cs Perovskites Driven by Natural Gradient Annealing

Low-bandgap formamidinium-cesium (FA-Cs) perovskites of FA1-xCsxPbI3 (x<0.1) are promising candidates for efficient and robust perovskite solar cells, but their black-phase crystallization is very sensitive to annealing temperature. Unfortunately, the low heat conductivity of the glass substrate builds up a temperature gradient within from bottom to top and makes the initial annealing temperature of the perovskite film lower than the black-phase crystallization point (~150°C). Herein, we take advantage of such temperature gradient for the diffusional growth of high-quality FA-Cs perovskites by introducing a thermally unstable MA+ cation, which would firstly form α-phase FA-MA-Cs mixed perovskites with low formation energy at the hot bottom of the perovskite films in the early annealing stage. The natural gradient annealing temperature and the thermally unstable MA+ cation then lead to the bottom-to-top diffusional growth of highly orientated α-phase FA-Cs perovskite, which exhibits 10-fold of enhanced crystallinity and reduced trap density (~3.85×1015 cm−3). Eventually, such FA-Cs perovskite films were fabricated into stable solar cell devices with champion efficiency up to 23.11%, among the highest efficiency of MA-free perovskite solar cells.

Effect of Graphene, SiO2 and Zeolite Powder on the Mechanical and Scratch Properties of PP

Scratch resistant surface of polypropylene (PP) is of critical importance for automobile, household appliances and other industries. In this paper, the mechanical and scratch properties of PP were studied by incorporation of three types of inorganic particles, including graphene (GP), silicon dioxide (SiO2) and zeolite powder (ZP), respectively. Maleic anhydride grafted polypropylene was used as compatibilizer. The effects of inorganic particle content on crystallization, mechanical properties and scratch resistance of PP composites were studied. Results showed that adding inorganic fillers led to enhanced crystallinity of PP, thus improving the scratch resistance of PP materials. Compared with PP/SiO2 and PP/ ZP, PP/GP exhibited the best scratch resistance and low sensitivity to scratch deformation at 2 wt% filler. We believe that the scratch resistance of PP was determined by material characteristics and crystallinity. This will be a reference for the research on the scratch resistance of other polymer materials.

Efficient Two-Dimensional Perovskite Solar Cells Realized by Incorporation of Ti3C2Tx MXene as Nano-Dopants

Two-dimensional (2D) perovskites solar cells (PSCs) have attracted considerable attention owing to their excellent stability against humidity; however, some imperfectness of 2D perovskites, such as poor crystallinity, disordered orientation, and inferior charge transport still limit the power conversion efficiency (PCE) of 2D PSCs. In this work, 2D Ti3C2Tx MXene nanosheets with high electrical conductivity and mobility were employed as a nanosized additive to prepare 2D Ruddlesden–Popper perovskite films. The PCE of solar cells was increased from 13.69 (without additive) to 15.71% after incorporating the Ti3C2Tx nanosheets with an optimized concentration. This improved performance is attributed to the enhanced crystallinity, orientation, and passivated trap states in the 3D phase that result in accelerated charge transfer process in vertical direction. More importantly, the unencapsulated cells exhibited excellent stability under ambient conditions with 55 ± 5% relative humidity.

Enhanced Crystallinity and Luminescence Characteristics of Hexagonal Boron Nitride Doped with Cerium Ions According to Tempering Temperatures

Hexagonal boron nitride was synthesized by pyrolysis using boric acid and melamine. At this time, to impart luminescence, rare earth cerium ions were added to synthesize hexagonal boron nitride nanophosphor particles exhibiting deep blue emission. To investigate the changes in crystallinity and luminescence according to the re-heating temperature, samples which had been subjected to pyrolysis at 900 °C were subjected to re-heating from 1100 °C to 1400 °C. Crystallinity and luminescence were enhanced according to changes in the reheating temperature. The synthesized cerium ion-doped hexagonal boron nitride nanoparticle phosphor was applied to the anti-counterfeiting field to prepare an ink that can only be identified under UV light.

Photocatalytic green synthesis of benzazoles from alcohol oxidation/toluene sp3 C-H activation over metal-free BCN: effect of crystallinity and N-B pairs exposure

Porous borocarbonitride (P-BCN), with characteristics of enhanced crystallinity and improved N-B pairs exposure, were prepared with simple KCl-assisted molten salt strategy. Efficient heterogeneous photocatalytic tandem synthesis of benzazoles from alcohol...