Rapid development of both efficiency 1 and stability 2 mean that perovskite solar cells are at the forefront of emerging photovoltaic technologies. State-of-the-art cells exhibit voltage losses 3-8 approaching the theoretical minimum and near-unity internal quantum efficiency 9-13 , but conversion efficiencies are limited by the fill-factor (FF < 83%, below the Shockley-Queisser limit of ~90%). This limitation results from non-ideal charge transport between the perovskite absorber and the cell's electrodes 5,8,13-16 . Reducing the electrical series resistance of charge transport layers is therefore crucial for improving efficiency. Here we introduce a reverse-doping process to fabricate nitrogen-doped titanium oxide electron transport layers with outstanding charge transport performance. By incorporating this charge transport material into perovskite solar cells, we demonstrate 1cm 2 cells with FFs >86%, and an average FF ~ 85.3%. We also report a certified steady-state efficiency record of 22.6% for a 1cm 2 cell (23.33% ± 0.58% from reverse current-voltage scan).Nitrogen-doped titanium oxide (titanium oxynitride, TiO x N y ) has been widely investigated for photocatalysis 17,18 , but rarely in perovskite solar cells (PSCs). PSCs incorporating solution-processed TiO x N y have been reported, but device performances have

A novel ternary nanocomposite electrolyte based on an ionic liquid electrolyte immobilized in a mesoporous SiO2 matrix is demonstrated in a solid‐state Li/TNCE/LiFePO4 battery configuration (see figure) to give solid‐state lithium ion batteries viable for practical applications. This specific solid‐state battery has the advantages of high energy/power density, good safety, low cost, flexible design, and environmental benignity.

We investigate the properties of an inexpensive hole-transporting material (HTM), copper phthalocyanine (CuPc), deposited by a solution-processing method in perovskite solar cells (PSCs). Cracks are found to be abundant on the as-deposited CuPc films, which lead to serious shunts and interface recombination. Surprisingly, shunts and interface recombination are significantly reduced and cell performance is greatly improved after heat treatment at 85 °C. We find that the enhancement is due to heat-induced migration of Au particles away from the cracks. Furthermore, Au is found to dope the CuPc film, and the doping effect is greatly enhanced by the heat treatment. Using CuPc and quadruple-cation perovskite, an efficiency of over 20% and negligible hysteresis is achieved after the heat treatment, which is the highest value reported for this structure. Additionally, PSCs employing CuPc and dual-cation perovskite show excellent thermal stability after >2000 h at 85 °C and good light stability at 25 °C.

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Here we present a simple yet powerful approach for the imaging of nanostructures under an optical microscope with the help of vapor condensation on their surfaces. Supersaturated water vapor will first form a nanometer-sized water droplet on the condensation nuclei on the surface of nanostructures, and then the water droplet will grow bigger and scatter more light to make the outline of the nanostructure be visible under dark-field optical microscope. This vapor-condensation-assisted (VCA) optical microscopy is applicable to a variety of nanostructures from ultralong carbon nanotubes to functional groups, generating images with contrast coming from the difference in density of the condensation sites, and does not induce any impurities to the specimens. Moreover, this low-cost and efficient technique can be conveniently integrated with other facilities, such as Raman spectroscope and so forth, which will pave the way for widespread applications.

Two-dimensional (2D) magnetic materials have attracted much attention due to their unique magnetic properties and promising applications in spintronics. Here, we report on the growth of ferrous chloride (FeCl2) films on Au(111) and graphite with atomic thickness by molecular-beam epitaxy (MBE) and the layer-dependent magnetic properties by density functional theory (DFT) calculations. The growth follows a layer-by-layer mode with adjustable thickness from sub-monolayer to a few layers. Four types of moiré superstructures of a single-layer FeCl2 on graphite and two types of atomic vacancies on Au(111) have been identified based on high-resolution scanning tunneling microscopy (STM). It turned out that the single- and few-layer FeCl2 films grown on Au(111) exhibit a 1T structure. The DFT calculations reveal that a single-layer 1T-FeCl2 has a ferromagnetic ground state. The minimum-energy configuration of a bilayer FeCl2 is satisfied for the 1T–1T structure with ferromagnetic layers coupled antiferromagnetically. These results make FeCl2 a promising candidate as ideal electrodes for spintronic devices providing large magnetoresistance.

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