The easily tunable emission of halide perovskite nanocrystals throughout the visible spectrum makes them an extremely promising material for light-emitting applications. Whereas high quantum yields and long-term colloidal stability have already been achieved for nanocrystals emitting in the red and green spectral range, the blue region currently lags behind with low quantum yields, broad emission profiles, and insufficient colloidal stability. In this work, we present a facile synthetic approach for obtaining two-dimensional CsPbBr nanoplatelets with monolayer-precise control over their thickness, resulting in sharp photoluminescence and electroluminescence peaks with a tunable emission wavelength between 432 and 497 nm due to quantum confinement. Subsequent addition of a PbBr-ligand solution repairs surface defects likely stemming from bromide and lead vacancies in a subensemble of weakly emissive nanoplatelets. The overall photoluminescence quantum yield of the blue-emissive colloidal dispersions is consequently enhanced up to a value of 73 ± 2%. Transient optical spectroscopy measurements focusing on the excitonic resonances further confirm the proposed repair process. Additionally, the high stability of these nanoplatelets in films and to prolonged ultraviolet light exposure is shown.

The colloidal synthesis and assembly of semiconductor nanowires continues to attract a great deal of interest. Herein, we describe the single-step ligand-mediated synthesis of single-crystalline CsPbBr perovskite nanowires (NWs) directly from the precursor powders. Studies of the reaction process and the morphological evolution revealed that the initially formed CsPbBr nanocubes are transformed into NWs through an oriented-attachment mechanism. The optical properties of the NWs can be tuned across the entire visible range by varying the halide (Cl, Br, and I) composition through subsequent halide ion exchange. Single-particle studies showed that these NWs exhibit strongly polarized emission with a polarization anisotropy of 0.36. More importantly, the NWs can self-assemble in a quasi-oriented fashion at an air/liquid interface. This process should also be easily applicable to perovskite nanocrystals of different morphologies for their integration into nanoscale optoelectronic devices.

Self-assembly of nanoscale building blocks into ordered nanoarchitectures has emerged as a simple and powerful approach for tailoring the nanoscale properties and the opportunities of using these properties for the development of novel optoelectronic nanodevices. Here, the one-pot synthesis of CsPbBr perovskite supercrystals (SCs) in a colloidal dispersion by ultrasonication is reported. The growth of the SCs occurs through the spontaneous self-assembly of individual nanocrystals (NCs), which form in highly concentrated solutions of precursor powders. The SCs retain the high photoluminescence (PL) efficiency of their NC subunits, however also exhibit a redshifted emission wavelength compared to that of the individual nanocubes due to interparticle electronic coupling. This redshift makes the SCs pure green emitters with PL maxima at ≈530-535 nm, while the individual nanocubes emit a cyan-green color (≈512 nm). The SCs can be used as an emissive layer in the fabrication of pure green light-emitting devices on rigid or flexible substrates. Moreover, the PL emission color is tunable across the visible range by employing a well-established halide ion exchange reaction on the obtained CsPbBr SCs. These results highlight the promise of perovskite SCs for light emitting applications, while providing insight into their collective optical properties.

The photoreduction of CO 2 on inorganic semiconductors has been researched for several decades, but the conversion efficiency is still low due to the recombination of photo-generated electron-hole pairs, low utilization efficiency of solar energy and weak adsorption of CO 2 . Here we for the first time demonstrate that metal-organic frameworks such as ZIF-8 can effectively adsorb CO 2 dissolved in water, and promote photocatalytic activity of a semiconductor catalyst in CO 2 reduction into liquid fuels in an aqueous medium. In particular, Zn 2 GeO 4 /ZIF-8 hybrid nanorods were successfully synthesized by growing ZIF-8 nanoparticles on Zn 2 GeO 4 nanorods. The Zn 2 GeO 4 /ZIF-8 nanocomposite inherits both high CO 2 adsorption capacity of ZIF-8 nanoparticles and high crystallinity of Zn 2 GeO 4 nanorods. The Zn 2 GeO 4 /ZIF-8 hybrid nanorods containing 25 wt% ZIF-8 exhibit 3.8 times higher dissolved CO 2 adsorption capacity than the bare Zn 2 GeO 4 nanorods, resulting in a 62% enhancement in photocatalytic conversion of CO 2 into liquid CH 3 OH fuel. The strategy reported here is promising for developing more active photocatalysts for improving CO 2 conversion efficiency by taking advantage of excellent adsorption property of metal-organic frameworks in aqueous media.