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Organolead halide perovskite solar cells (PSC) are arising as promising candidates for next-generation renewable energy conversion devices. Currently, inverted PSCs typically employ expensive organic semiconductor as electron transport material and thermally deposited metal as cathode (such as Ag, Au, or Al), which are incompatible with their large-scale production. Moreover, the use of metal cathode also limits the long-term device stability under normal operation conditions. Herein, a novel inverted PSC employs a SnO 2 -coated carbon nanotube (SnO 2 @CSCNT) film as cathode in both rigid and flexible substrates (substrate/NiO-perovskite/Al 2 O 3 -perovskite/SnO 2 @ CSCNT-perovskite). Inverted PSCs with SnO 2 @CSCNT cathode exhibit considerable enhancement in photovoltaic performance in comparison with the devices without SnO 2 coating owing to the significantly reduced charge recombination. As a result, a power conversion efficiency of 14.3% can be obtained on rigid substrates while the flexible ones achieve 10.5% efficiency. More importantly, SnO 2 @CSCNT-based inverted PSCs exhibit significantly improved stability compared to the standard inverted devices made with silver cathode, retaining over 88% of their original efficiencies after 550 h of full light soaking or thermal stress. The results indicate that SnO 2 @CSCNT is a promising cathode material for long-term device operation and pave the way toward realistic commercialization of flexible PSCs.

Summary In Streptomyces, GlnR is an activator protein that activates nitrogen‐assimilation genes under nitrogen‐limiting conditions. However, less is known regarding the regulation of these genes under nitrogen‐rich conditions. We determined that the developmental regulator MtrA represses nitrogen‐assimilation genes in nitrogen‐rich media and that it competes with GlnR for binding to GlnR boxes. The GlnR boxes upstream of multiple nitrogen genes, such as amtB, were confirmed as MtrA binding sites in vitro by electrophoretic mobility shift assays and in vivo by ChIP‐qPCR analysis. Transcriptional analysis indicated that, on nutrient‐rich medium, MtrA profoundly repressed expression of nitrogen‐associated genes, indicating opposing roles for MtrA and GlnR in the control of nitrogen metabolism. Using in vitro and in vivo analysis, we also showed that glnR is itself a direct target of MtrA and that MtrA represses glnR transcription. We further demonstrated functional conservation of MtrA homologues in the recognition of GlnR boxes upstream of nitrogen genes from different actinobacterial species. As mtrA and glnR are widespread among actinomycetes, this mechanism of potential competitive control over nitrogen metabolism genes may be common in this group, adding a major new layer of complexity to the known regulatory network for nitrogen metabolism in Streptomyces and related species.

To tackle the aggravating electromagnetic wave (EMW) pollution issues, high-efficiency EMW absorption materials are urgently explored. Metal–organic framework (MOF) derivatives have been intensively investigated for EMW absorption due to the distinctive components and structures, which is expected to satisfy diverse application requirements. The extensive developments on MOF derivatives demonstrate its significantly important role in this research area. Particularly, MOF derivatives deliver huge performance superiorities in light weight, broad bandwidth, and robust loss capacity, which are attributed to the outstanding impedance matching, multiple attenuation mechanisms, and destructive interference effect. Herein, we summarized the relevant theories and evaluation methods, and categorized the state-of-the-art research progresses on MOF derivatives in EMW absorption field. In spite of lots of challenges to face, MOF derivatives have illuminated infinite potentials for further development as EMW absorption materials.