Tin-based perovskites with low toxicity and a narrow band gap have been promising candidates for the fabrication of efficient lead-free perovskite solar cells (PSCs). Nevertheless, the power conversion efficiency (PCE) of tin-based PSCs still lags behind that of their lead counterparts due to the poor film quality induced by uncontrollable crystal growth and Sn 2+ self-doping. Herein, we introduce a bifunctional additive, ammonium thiocyanate (NH 4 SCN), into the precursor solution, which is able to coordinate with SnI 2 to effectively control the crystal growth of the FASnI 3 perovskite and further passivate the trap states in the perovskite films. Furthermore, the modified FASnI 3 perovskite displays an improved film quality, featuring a compact surface morphology with an enlarged grain size, as well as decreased trap density, resulting in the reduction of the Sn 4+ /Sn 2+ proportion in the film. As a result, a considerably enhanced PCE from 4.45 to 8.15% has been demonstrated. More importantly, the NH 4 SCN-based device exhibits advanced environment stability, retaining over 70% of the initial efficiency after 100 h of exposure to 35 ± 5% relative humidity at room temperature in a dark environment. This finding provides an additive strategy to improve the efficiency and stability of tin-based PSCs.

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In order to solve the data protection problem of STL model, this paper proposes a 3D printing watermarking method based on Menger curvature and K-means clustering algorithm. By comparing the research contents of 3D mesh model watermarking algorithm and two 3D printing watermarking methods, the 3D printing watermarking method is applied based on Menger curvature and K-means clustering algorithm. The method flow, watermark embedding and watermark extraction are discussed. Finally, the experimental results show that this method can not only improve the invisibility of model watermark, but also be robust to geometric attacks such as rotation, scaling and translation.

Nano-materials are ultra-fine materials with nano-sized particles, and their unique structure also makes nano-materials have different physical and chemical properties. Nano-materials can be added to a variety of lubricants, play a good anti-wear and anti-friction effect, and can be used in many fields, such as bearing lubrication, gear transmission, cutting processing. At present, the types of nano-lubricating additives include metal element nanoparticles, oxide and hydroxide nanoparticles, nano-carbide and its derivatives, nano-sulfide, nano-rare-earth compound, nano-boron series, polymer nano-beads, etc. This article reviews the research status of nano lubricating additives.