Perovskite solar cells have received considerable attention in recent years as a promising material capable of developing high performance photovoltaic devices at a low cost. Its high absorption coefficient, tunable band gap, low temperature processing and abundant elemental constituents provide numerous advantages over most thin film absorber materials. In this feature article, we discuss the current status of CH3NH3PbX3 (X = I, Br, Cl) based photovoltaic devices and provide a comprehensive review of CH3NH3PbX3 device structures, film properties, fabrication methods, and photovoltaic performance. We emphasize the importance of perovskite film formation and properties in achieving highly efficient photovoltaic devices. The flexibility and simplicity of perovskite fabrication methods allow use of mesoporous and planar device architectures. A variety of processing techniques are currently employed to form the highest quality CH3NH3PbX3 films that include precursor modifications, thermal annealing and post-deposition treatments. Here we outline and discuss the resulting material qualities and device performances. Suggestions regarding needed improvements and future research directions are provided based on the current field of available literature.

Iridescent films composed of the chiral nematic liquid crystal phase of cellulose nanocrystals (CNC) have attracted significant interest due to their fascinating optical properties. However, the current fabrication method, i.e., solution casting with a subsequent evaporation process, has significant limitations and therefore hinders the application of CNC iridescent films. In the present study, we demonstrate, for the first time, that vacuum-assisted self-assembly (VASA) can be used to fabricate highly oriented, large area, smooth, and structurally homogeneous CNC iridescent films. It was found that a long ultrasonic pretreatment is necessary for obtaining CNC iridescent films via VASA. Furthermore, it was also found that the iridescent color of the CNC films can be tuned by the sonication time, suspension volume, and degree of vacuum. By combining CD spectroscopy, SEM, and WAXD techniques, the internal structure of CNC iridescent films prepared by VASA has been investigated in detail. Moreover, the origin of the ultrasonic pretreatment effect on the self-assembly behavior of CNCs is also discussed.

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Organic–inorganic hybrid perovskite solar cells (PSCs) have demonstrated high efficiency and improved stability, which shows promising potential for commercialization. However, among all challenges, the material and device instability of the methylammonium lead iodide (MAPbI3) absorber are regarded as serious obstacles to the future development of devices for long‐term operation. Compared with conventional MAPbI3, formamidinium lead iodide (FAPbI3) and cesium lead iodide (CsPbI3) have attracted more attention due to their superior thermal stability. Due to their undesirable tolerant factor, however, these materials suffer from poor phase stability, which is worthy of careful investigation. This perspective highlights the recent progress on the phase stabilization of FAPbI3 and inorganic CsPbI3 materials with emphasis on the fundamental understanding of the origin of phase instability. In addition, strategies to fabricate corresponding devices toward high‐efficiency and long‐lifetime are discussed. This review sheds light onto the design and synthesis of FAPbI3 and inorganic CsPbI3 perovskite materials. In the end, the potential of FAPbI3 and inorganic CsPbI3 perovskite materials as stable absorbers is discussed, which promotes the development of corresponding solar cells and other optoelectronic devices for practical applications.

Nanopores fabricated from synthetic materials (solid-state nanopores), platforms for characterizing biological molecules, have been widely studied among researchers. Compared with biological nanopores, solid-state nanopores are mechanically robust and durable with a tunable pore size and geometry. Solid-state nanopores with sizes as small as 1.3 nm have been fabricated in various films using engraving techniques, such as focused ion beam (FIB) and focused electron beam (FEB) drilling methods. With the demand of massively parallel sensing, many scalable fabrication strategies have been proposed. In this review, typical fabrication technologies for solid-state nanopores reported to date are summarized, with the advantages and limitations of each technology discussed in detail. Advanced shrinking strategies to prepare nanopores with desired shapes and sizes down to sub-1 nm are concluded. Finally, applications of solid-state nanopores in DNA sequencing, single molecule detection, ion-selective transport, and nanopatterning are outlined.