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All inorganic perovskite nanocrystals (NCs) of CsPbX (X = Cl, Br, I, or their mixture) are regarded as promising candidates for high-performance light-emitting diode (LED) owing to their high photoluminescence (PL) quantum yield (QY) and easy synthetic process. However, CsPbX NCs synthesized by the existing methods, where oleic acid (OA) and oleylamine (OLA) are generally used as surface-chelating ligands, suffer from poor stability due to the ligand loss, which drastically deteriorates their PL QY, as well as dispersibility in solvents. Herein, the OA/OLA ligands are replaced with octylphosphonic acid (OPA), which dramatically enhances the CsPbX stability. Owing to a strong interaction between OPA and lead atoms, the OPA-capped CsPbX (OPA-CsPbX) NCs not only preserve their high PL QY (>90%) but also achieve a high-quality dispersion in solvents after multiple purification processes. Moreover, the organic residue in purified OPA-CsPbBr is only ∼4.6%, which is much lower than ∼29.7% in OA/OLA-CsPbBr. Thereby, a uniform and compact OPA-CsPbBr film is obtained for LED application. A green LED with a current efficiency of 18.13 cd A, corresponding to an external quantum efficiency of 6.5%, is obtained. Our research provides a path to prepare high-quality perovskite NCs for high-performance optoelectronic devices.

Research has found that political connectedness can have both positive and negative effects on firm value. To resolve these mixed findings, we investigate the impact of political ties conditional on ownership for a sample of Chinese firms over the period [1999][2000][2001][2002][2003][2004][2005][2006]. We find that private firms with politically connected managers have a higher value and obtain more government subsidies than those without connected managers, whereas local state-owned enterprises with connected managers have a lower value and employ more surplus labour than those without connected managers. Our results indicate that the effect of political ties is subject to firm ownership.

All-inorganic perovskite light-emitting diodes (LEDs) reveal efficient luminescence with high color purity, but their modest brightness and poor stability are still critical drawbacks. Here, the luminescent efficiency and the stability of perovskite LEDs (PeLEDs) are boosted by antisolvent vapor treatment of CsPbBr 3 embedded in a dielectric polymer matrix of polyethylene oxide (PEO). A unique method is developed to obtain high quality CsPbBr 3 emitting layers with low defects by controlling their grain sizes. CsPbBr 3 in PEO matrix is post-treated with antisolvent of chloroform (CF), leading to microcrystals with a size of ≈5 µm along the in-plane direction with active emitting composite of 90%. A device based on CF post-treatment (CsPbBr 3 -PEO-CF) film displays a brightness of up to 51890 cd m −2 with an external quantum efficiency of 4.76%. CsPbBr 3 -PEO-CF PeLED still maintains 82% of its initial efficiency after 80 h continuous operation in ambient air, which indicates relatively good device stability. This work highlights that film quality is not only key to promoting fluorescence in CsPbBr 3 , but also to achieving higher performance PeLEDs.

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