Mg doping improves interfacial contact and endows low hysteresis high temperature processed SnO2-based PSCs with a steady-state PCE of 14.55%.

Planar perovskite solar cells (PSCs) based on low-temperature-processed (LTP) SnO 2 have demonstrated excellent photovoltaic properties duo to the high electron mobility, wide bandgap, and suitable band energy alignment of LTP SnO 2 . However, planar PSCs or mesoporous (mp) PSCs based on hightemperature-processed (HTP) SnO 2 show much degraded performance. Here, a new strategy with fully HTP Mg-doped quantum dot SnO 2 as blocking layer (bl) and a quite thin SnO 2 nanoparticle as mp layer are developed. The performances of both planar and mp PSCs has been greatly improved. The use of Mg-SnO 2 in planar PSCs yields a high-stabilized power conversion efficiency (PCE) of close to 17%. The champion of mp cells exhibits hysteresis free and stable performance with a high-stabilized PCE of 19.12%. The inclusion of thin mp SnO 2 in PSCs not only plays a role of an energy bridge, facilitating electrons transfer from perovskite to SnO 2 bl, but also enhances the contact area of SnO 2 with perovskite absorber. Impedance analysis suggests that the thin mp layer is an "active scaffold" selectively collecting electrons from perovskite and can eliminate hysteresis and effectively suppress recombination. This is an inspiring advance toward high-performance PSCs with HTP mp SnO 2 .

Metal selenides have great potential for electrochemical energy storage, but are relatively scarce investigated. Herein, a novel hollow core-branch CoSe nanoarray on carbon cloth is designed by a facile selenization reaction of predesigned CoO nanocones. And the electrochemical reaction mechanism of CoSe in supercapacitor is studied in detail for the first time. Compared with CoO, the hollow core-branch CoSe has both larger specific surface area and higher electrical conductivity. When tested as a supercapacitor positive electrode, the CoSe delivers a high specific capacitance of 759.5 F g at 1 mA cm , which is much larger than that of CoO nanocones (319.5 F g ). In addition, the CoSe electrode exhibits excellent cycling stability in that a capacitance retention of 94.5% can be maintained after 5000 charge-discharge cycles at 5 mA cm . An asymmetric supercapacitor using the CoSe as cathode and an N-doped carbon nanowall as anode is further assembled, which show a high energy density of 32.2 Wh kg at a power density of 1914.7 W kg , and maintains 24.9 Wh kg when power density increased to 7354.8 W kg . Moreover, the CoSe electrode also exhibits better oxygen evolution reaction activity than that of CoO.

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Porous CoSe on carbon cloth is prepared from a cobalt-based metal organic framework template with etching and selenization reaction, which has both a larger specific surface area and outstanding electrical conductivity. As the catalyst for oxygen evolution reaction, the porous CoSe achieves a lower onset potential of 1.48 V versus the reversible hydrogen electrode (RHE) and a small potential of 1.52 V (vs RHE) at an anodic current density of 10 mA cm. Especially, the linear sweep voltammogram curve of the porous CoSe is in consist with the initial curve after durability test for 24 h. When tested as an electrode for supercapacitor, it can deliver a specific capacitance of 713.9 F g at current density of 1 mA cm and exhibit excellent cycling stability in that a capacitance retention of 92.4% can be maintained after 5000 charge-discharge cycles at 5 mA cm. Our work presents a novel strategy for construction of electrochemical electrode.

Polymer solar cells (PSCs) with poly(3‐hexylthiophene) (P3HT) as a donor, an indene‐C70 bisadduct (IC70BA) as an acceptor, a layer of indium tin oxide modified by MoO3 as a positive electrode, and Ca/Al as a negative electrode are presented. The photovoltaic performance of the PSCs was optimized by controlling spin‐coating time (solvent annealing time) and thermal annealing, and the effect of the spin‐coating times on absorption spectra, X‐ray diffraction patterns, and transmission electron microscopy images of P3HT/IC70BA blend films were systematically investigated. Optimized PSCs were obtained from P3HT/IC70BA (1:1, w/w), which exhibited a high power conversion efficiency of 6.68%. The excellent performance of the PSCs is attributed to the higher crystallinity of P3HT and better a donor–acceptor interpenetrating network of the active layer prepared under the optimized conditions. In addition, PSCs with a poly(3,4‐ethylenedioxy‐thiophene):poly(styrenesulfonate) (PEDOT:PSS) buffer layer under the same optimized conditions showed a PCE of 6.20%. The results indicate that the MoO3 buffer layer in the PSCs based on P3HT/IC70BA is superior to that of the PEDOT:PSS buffer layer, not only showing a higher device stability but also resulting in a better photovoltaic performance of the PSCs.

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