One-Stone-for-Two-Birds Method to Improve the SnO2 Layers for High Power-per-Weight Flexible Perovskite Solar Cell Mini-modules.

Maintaining the power conversion efficiency (PCE) of flexible perovskite solar cells (fPSCs) while decreasing their weight is essential to utilize their lightweight and flexibility as much as possible for commercialization. Strengthening the interfaces between functional layers, such as flexible substrates, charge transport layers, and perovskite active layers, is critical to addressing the issue. Herein, we propose a feasible and one-stone-for-two-birds method to improve the electron transport layer (ETL), SnO2, and the interface between the ETL and perovskite layer simultaneously. In detail, poly(acrylate ammonium) (PAAm), a low-cost polymer with a long chain structure, is added into the SnO2 aqueous solution to reduce the aggregation of SnO2 nanoparticles, resulting in the deposition of a conformal and high-quality ETL film on the tin-doped indium oxide film surface. Simultaneously, PAAm addition can effectively regulate the crystallization of the perovskite films, strengthening the interface between the SnO2 film and the buried surface of the perovskite layer. The outstanding PCEs of 22.41% on small-scale fPSCs and 18.54% on fPSC mini-modules are among the state-of-the-art n-i-p type fPSCs. Moreover, the fPSC mini-module on the 20 µm-thick flexible substrate shows a comparable PCE with that of the fPSC mini-module on the 125 µm-thick flexible substrate, exhibiting a high power-to-weight of 5.097 W/g. This work provides an easy but essential direction for further applications of fPSCs in diverse scenarios.

Effect of magnetized water irrigation on Cd subcellular allocation and chemical forms in leaves of Festuca arundinacea during phytoremediation.

The application of an external magnetic field has been shown to improve the Cd phytoremediation efficiency of F. arundinacea by leaf harvesting. However, the influencing mechanisms of the promoting effect have not yet been revealed. This study evaluated variations in the Cd subcellular allocation and fractions in various F. arundinacea leaves, with or without magnetized water irrigation. Over 50 % of the metal were sequestered within the cell wall in all tissues under all treatments, indicating that cell wall binding was a critical detoxification pathway for Cd. After magnetized water treatment, the metal stored in the cytoplasm of roots raised from 33.1 % to 45.3 %, and the quantity of soluble Cd in plant roots enhanced from 53.4 % to 59.0 %. The findings suggested that magnetized water mobilized Cd in the roots, and thus drove it into the leaves. In addition, the proportion of Cd in the organelles, and the concentration of ethanol-extracted Cd in emerging leaves, decreased by 13.0 % and 47.1 %, respectively, after magnetized water treatment. These results explained why an external field improved the phytoextraction effect of the plant through leaf harvesting.

How to Stabilize the Current of Efficient Inverted Flexible Perovskite Solar Cells at the Maximum Power Point.

Inverted flexible perovskite cells (fPSCs) have attracted much attention for their high efficiency and power per weight. Still, the steady-state output is one of the critical factors for their commercialization. In this paper, it is found that the steady-state current of inverted fPSCs based on nickel oxide nanoparticles (n-NiOx) continuously decreases under light illumination. Conversely, those based on magnetron-sputtered NiOx (sp-NiOx) exhibit the opposite result. Based on visualization of ion migration in the photoluminescence (PL) imaging microscopy tests, the discrepancies in the buried surfaces lead to the differences in ion migration in perovskite films, which triggers the temporary instability of the output current of devices during operation. The DFT theoretical calculation and experimental results reveal that NiOx films with different contents of Ni vacancies can modulate the crystallization of the perovskite films on the NiOx surfaces. Tuning the crystallization of the perovskite films is essential to stabilize the output current of fPSCs at a steady state. To demonstrate that, capsaicin is doped into the perovskite solutions to improve the quality of the perovskite buried interface. Finally, the corresponding fPSCs exhibit outstanding efficiency and stability during operation. These results provide valuable scientific guidance for fabricating fPSCs with stable operation under illumination conditions.

A "time-frozen" technique in microchannel used for the thermodynamic studies of DNA origami.

The emergence of DNA origami greatly accelerated the development of DNA nanotechnology. A thorough understanding of origami thermodynamics is very important for both fundamental studies and practical applications. These thermodynamic transitions usually take place in several seconds or even less, and are very difficult to monitor by conventional methods. Numerous tests are required to characterize the origami molecule's behaviors at different temperatures, which is very labor-intensive and time-consuming. In this paper, an axially distributed temperature gradient along a capillary was formed in a spatially varying temperature field. In such a temperature gradient, the origami molecule's thermodynamic processes occur and remain stable at every position along the capillary's microchannel. It looks like the time of the thermodynamic process is frozen along the microchannel. With this method, the origami molecule's thermodynamic characteristics at different temperatures can be obtained in a single experiment, and rapid processes can be monitored with ease by conventional methods for an adequate time period at low cost. In order to show its potential abilities, this method has been demonstrated in applications which the origami's assembly, denaturation and strand displacement are carry out in a flowing or stationary solution.

Low-Cost Automatic Sensor for in Situ Colorimetric Detection of Phosphate and Nitrite in Agricultural Water.

This study proposed a low-cost sensor for in situ automatic monitoring of phosphate and nitrite in agricultural water environments, involving a series of "Fish-Bite" reservoirs, multiple reagent capsules, and a colorimetric sensor. The Fish-Bite reservoir is an alternative to the pumps, valves, and filters that are widely used for water sample collection and also offers a closed cell for chromogenic reactions afterward. Up to two capsules can be embedded in each reservoir to support chromogenic reactions that use two different reagents in sequence. From the results of calibration tests in the laboratory, the limit of detection was found to be approximately 0.01 mg/L for both phosphate and nitrite, with a linear range of 0.01-1.00 mg/L for phosphate and 0.01-0.20 mg/L for nitrite. Furthermore, an in situ experiment was successfully carried out in an irrigation canal beside farmland to demonstrate the practicability and robustness of the device. The averaged concentrations of phosphate and nitrite were 0.0113 mg/L and 0.0383 mg/L, respectively. The relative deviations were 20.2% and 11.7%, respectively, referred to results obtained by using the standard spectrophotometric methods. With the advantages of being robust, fast, and low cost, this in situ device is promising for the formation of agricultural sensor networks.