CsPbI3 perovskite quantum dots (QDs) are more unstable over time as compared to other perovskite QDs, owing to ligand loss and phase transformation. The strong red emission from fresh CsPbI3 QDs gradually declines to a weak emission from aged QDs, which PLQY dropped by 93% after a 20 day storage; finally, there is no emission from δ-phase CsPbI3. The present study demonstrated a facile surface treatment method, where a sulfur–oleylamine (S-OLA) complex was utilized to passivate the defect-rich surface of the CsPbI3 QDs and then self-assembly to form a matrix outside the CsPbI3 QDs protected the QDs from environmental moisture and solar irradiation. The PLQY of the treated CsPbI3 QDs increased to 82.4% compared to initial value of 52.3% of the fresh QDs. Furthermore, there was a significant increase in the colloidal stability of the CsPbI3 QDs. Above 80% of the original PLQY of the treated QDs was reserved after a 20 day storage and the black phase could be maintained for three months before transforming to the yellow phase. The introduction of S-OLA induced the recovery of the lost photoluminescence of the nonluminous aged CsPbI3 QDs with time to 95% of that of the fresh QDs. Furthermore, the photoluminescence was maintained for one month. The increase in the stability and photoluminescence are critical for realizing high-performance perovskite-QD-based devices. Therefore, this work paves the way for increasing the performance of perovskite-based devices in the near future.

Organic–inorganic metal halide perovskites (HPs) have emerged as new frontier materials for optoelectronic and energy applications. In addition to various well‐known applications, such as solar cells, light‐emitting diodes, photodetectors, and resistive switching memories, HPs can be utilized as efficient photocatalysts for numerous electrochemical reactions, including carbon dioxide (CO2) reduction reactions, hydrogen evolution reaction, photosynthesis, and wastewater treatment. However, the use of HPs toward photo‐driven catalysis remains a tremendous challenge owing to their poor stability in polar solvents. Nevertheless, huge progress has been made to counter this critical issue for improving the performance of HPs as efficient photocatalysts in a wide range of applications. In this review, we first introduce the structures and properties of HPs. Next, we highlight the recent approaches on the fabrication of HPs, including thin films and nanostructures. Strategies for implementing HPs in catalysis systems and their working mechanisms are thoroughly summarized and discussed. Lastly, the current challenges and prospects of the application of HPs toward photocatalytic reactions are fully addressed. © 2020 Society of Chemical Industry

Two-dimensional (2D) and quasi-2D (q-2D) halide perovskites (HPs) offer a number of advantages compared with their three-dimensional (3D) counterparts for electronic and optoelectronic applications due to their tunable properties and superior stability. This mini-Review, at first is focused on the atomic structure and the optical and electrical properties of 2D and q-2D HPs. The unique properties of 2D HPs are addressed in comparison with 3D HPs. Recent progress in applications using 2D and q-2D HPs is summarized, such as in solar cells, lightemitting diodes, photodetectors, resistive random access memories, and artificial synapses. The main parameters that regulate the device performance and strategies for improving materials properties and device performance for each application are addressed. Finally, the perspective for the future development of 2D and q-2D HPs is discussed.

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2D and quasi‐2D halide perovskites show a number of advantages for electronic and optoelectronic applications due to their tunable properties and superior stability. In article number http://doi.wiley.com/10.1002/pssr.201900435, Quyet Van Le, Ho Won Jang and co‐workers review the atomic structures, optical properties, and electrical properties of 2D and quasi‐2D halide perovskites compared to their 3D counterparts. The authors summarize recent progress in applications using 2D and quasi‐2D halide perovskites, such as solar cells, light emitting diodes, photodetectors, resistive random access memories, and artificial synapses. Main parameters that regulate the device performance are addressed, as well as strategies for improving materials properties and device performance for each application.

In this work, a facile sol-gel and annealing technique was employed to prepare amorphous electrochromic tungsten oxide thin films at a relatively low temperature. Specifically, ammonium metatungstate hydrate was blended in dimethylformamide and was used as the precursor for obtaining highly uniform and transparent amorphous WO x by simple spin-coating and calcining in ambient air at 250 C for 2 hours. The film exhibits an unprecedented stability over 4000 operational cycles with a high coloration efficiency of 125 cm 2 C −1 and fast switching times of 5 seconds for the colored state and 2.5 seconds for the bleaching state. Therefore, the prepared amorphous tungsten oxide film is a prominent material for the next generation of electrochromic devices that can be used in smart windows and electronic display devices.

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