Removal of organics by combined process of coagulation–chlorination–ultrafiltration: optimization of overall operation parameters

<p>To gain the run parameters of the combined process of coagulation/<i>in situ</i> chlorination/ultrafiltration (UF) so that the system can remove as much organic contaminants as possible without serious membrane fouling, the impacts of operation conditions in coagulation and pre-chlorination unit were investigated in a pilot-scale test. The characteristics of organics in UF influent were examined by excitation emission matrix spectroscopy to find out fouling behavior of different natural organic matter compositions to UF membrane. Thereafter, the operation parameters of different processing units of the hybrid device were optimized by response surface methodology (RSM). The results showed that the tests with the agitation speed of 40 r min⁻¹ had the lowest membrane fouling rate and the highest COD_Mn removal, in addition, inappropriate dosage of sodium hypochlorite in membrane influent might exert negative impacts on membrane by lowering UV₂₅₄ rejection, especially during the high algae laden period. The predominant factors of membrane fouling were the existence of tryptophan protein-like substances and the soluble microbial products. Optimum values of the mechanical rotation speed in coagulation unit, chemical dosage in pre-chlorination unit, and membrane flux in UF unit of the integrative process were 41.79 r min⁻¹, 1.40 mg L⁻¹, and 82.26 LMH, respectively.</p

Cation Dynamics Governed Thermal Properties of Lead Halide Perovskite Nanowires

Metal halide perovskite (MHP) nanowires such as hybrid organic–inorganic CH₃NH₃PbX₃ (X = Cl, Br, I) have drawn significant attention as promising building blocks for high-performance solar cells, light-emitting devices, and semiconductor lasers. However, the physics of thermal transport in MHP nanowires is still elusive even though it is highly relevant to the device thermal stability and optoelectronic performance. Through combined experimental measurements and theoretical analyses, here we disclose the underlying mechanisms governing thermal transport in three different kinds of lead halide perovskite nanowires (CH₃NH₃PbI₃, CH₃NH₃PbBr₃ and CsPbBr₃). It is shown that the thermal conductivity of CH₃NH₃PbBr₃ nanowires is significantly suppressed as compared to that of CsPbBr₃ nanowires, which is attributed to the cation dynamic disorder. Furthermore, we observed different temperature-dependent thermal conductivities of hybrid perovskites CH₃NH₃PbBr₃ and CH₃NH₃PbI₃, which can be attributed to accelerated cation dynamics in CH₃NH₃PbBr₃ at low temperature and the combined effects of lower phonon group velocity and higher Umklapp scattering rate in CH₃NH₃PbI₃ at high temperature. These data and understanding should shed light on the design of high-performance MHP based thermal and optoelectronic devices

Scalable processing for realizing 21.7%-efficient all-perovskite tandem solar modules.

10.1126/science.abn7696Science3766594762-76

Oxidation-resistant all-perovskite tandem solar cells in substrate configuration

The superstate configuration in all-perovskite tandem solar cells is disadvantageous for long-term stability. Here, the authors reverse the processing order and demonstrate substrate configuration to bury oxidizable narrow-bandgap perovskites, and achieve efficiency of 25.3% with long stability

All-perovskite tandem solar cells with 24.2% certified efficiency and area over 1 cm2 using surface-anchoring zwitterionic antioxidant

Monolithic all-perovskite tandem solar cells offer an avenue to increase power conversion efficiency beyond the limits of single-junction cells. It is an important priority to unite efficiency, uniformity and stability, yet this has proven challenging because of high trap density and ready oxidation in narrow-bandgap mixed lead–tin perovskite subcells. Here we report simultaneous enhancements in the efficiency, uniformity and stability of narrow-bandgap subcells using strongly reductive surface-anchoring zwitterionic molecules. The zwitterionic antioxidant inhibits Sn2+ oxidation and passivates defects at the grain surfaces in mixed lead–tin perovskite films, enabling an efficiency of 21.7% (certified 20.7%) for single-junction solar cells. We further obtain a certified efficiency of 24.2% in 1-cm2-area all-perovskite tandem cells and in-lab power conversion efficiencies of 25.6% and 21.4% for 0.049 cm2 and 12 cm2 devices, respectively. The encapsulated tandem devices retain 88% of their initial performance following 500 hours of operation at a device temperature of 54–60 °C under one-sun illumination in ambient conditions.This work is financially supported by the National Natural Science Foundation of China (61974063, 61921005), Fundamental Research Funds for the Central Universities (14380168), National Key R&D Program of China (2018YFB1500102), Natural Science Foundation of Jiangsu Province (BK20190315), Basic Research Program of Frontier Leading Technologies in Jiangsu Province, Program for Innovative Talents and Entrepreneur in Jiangsu and Thousand Talent Program for Young Outstanding Scientists in China. The work of Y.H., M.W. and E.H.S. is supported by US Department of the Navy, Office of Naval Research (N00014-20-1-2572). V.Y. and M.I.S. acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC)