Both broadband and narrowband organic photodetectors can be realized due to the easily tunable optical/electronic properties of organic semiconductors.

Halide substitution in phenethylammonium spacer cations (X‐PEA+, X = F, Cl, Br) is a facile strategy to improve the performance of PEA based perovskite solar cells (PSCs). However, the power conversion efficiency (PCE) of X‐PEA based quasi‐2D (Q‐2D) PSCs is still unsatisfactory and the underlying mechanisms are in debate. Here, the in‐depth study on the impact of halide substitution on the crystal orientation and multi‐phase distribution in PEA based perovskite films are reported. The halide substitution eliminates n = 1 2D perovskite and thus leads to the perpendicular crystal orientation. Furthermore, nucleation competition exists between small‐n and large‐n phases in PEA and X‐PEA based perovskites. This gives rise to the orderly distribution of different n‐phases in the PEA and F‐PEA based films, and random distribution in Cl‐PEA and Br‐PEA based films. As a result, (F‐PEA)2MA3Pb4I12 (MA = CH3NH3+, n = 4) based PSCs achieve a PCE of 18.10%, significantly higher than those of PEA (12.23%), Cl‐PEA (7.93%) and Br‐PEA (6.08%) based PSCs. Moreover, the F‐PEA based devices exhibit remarkably improved stability compared to their 3D counterparts.

Diradicaloids are promising materials for organic electronics and nonlinear optics due to their unique optical, electronic and magnetic properties. High performance organic field-effect transistor and photodetector based on diradicaloids have been achieved. Future potential applications in organic batteries, memory, logic gates and non-linear optics are expected.

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Topochemical Polymerization In a topochemical reaction, chemical changes start at active sites in the solid and then proceed autocatalytically to neighboring regions. If one starts with a monomer that can form ordered structures similar to the final polymer, it is possible to polymerize chains in a fully ordered state and thus make very long single chains. Dou et al. (p. 272 ; see the Perspective by Goroff ) describe an unexpected visible-light–induced polymerization of derivatives of a dye. Two of the derivatives underwent photoinduced single-crystal-to-single-crystal topochemical polymerization.

Radicals, organic molecules with unpaired electrons, are applied across different scientific disciplines such as electronics, energy storage and biochemistry.

Anti-icing and deicing are the two major pathways for suppressing adhesion of ice on surfaces, yet materials with dual capabilities are rare. In this work, we have designed a perfluorododecylated graphene nanoribbon (FDO-GNR) film that takes advantage of both the low polarizability of perfluorinated carbons and the intrinsic conductive nature of graphene nanoribbons. The FDO-GNR films are superhydrophobic with a sheet resistance below 8 kΩ·sq(-1) and then exhibit an anti-icing property that prevents freezing of incoming ice-cold water down to -14 °C. After that point, voltage can be applied to the films to resistively heat and deice the surface. Further a lubricating liquid can be employed to create a slippery surface to improve the film's deicing performance. The FDO-GNR films can be easily switched between the superhydrophobic anti-icing mode and the slippery deicing mode by applying the lubricant. A spray-coating method makes it suitable for large-scale applications. The anti-icing and deicing properties render the FDO-GNR films with promise for use in extreme environments.

Secret information recorded by traditional single-encrypted invisible inks is easily cracked because the inks can switch only between “NONE” and “TRUTH”. Developing double-encrypted systems makes the information reversibly switchable between “FALSE” and “TRUTH”, which is helpful to ensure the safety of the secret information during transport. Here, we prepared heat-developed invisible inks by hydrochromic molecules donor–acceptor Stenhouse adducts (DASAs) and oxazolidines (OXs) and promoted the invisible inks from single to double encryption. DASAs coordinate with water molecules and form stable colorless cyclic DASA·xH2O molecules, which lose coordinated water molecules after heating and switch to colored linear DASAs. In contrast, OXs are colored with water and are colorless after heating. Single-encrypted secrecy was realized by DASA invisible inks. The information is invisible under the encrypted state and becomes bright purple after heating. Vapor treating re-encrypted the information in ∼5 min. Furthermore, the single-encryption was promoted to double-encryption by a DASA/OX invisible inks system. Heating and vapor treating switch the information between the “FALSE” and “TRUTH” reversibly. The DASA/OX invisible ink system is applied for secrecy of texts, graphic images, and quick response (QR) codes.