Metal halides doping of perovskite nanocrystals (NCs) has been shown to precisely control nonradiative pathways and to improve photoluminescence quantum yield (PLQY). Here, we report a trivalent lanthanide halide neodymium (III) chloride (NdCl3)-doped perovskite NCs prepared with a post-synthetic room temperature treatment for efficient blue light-emitting devices (LEDs). The Nd 3d and Cl 2p core peaks were observed in the NdCl3-doped NCs, which allowed for simultaneous doping of Nd3+ and Cl– into the pristine CsPbBr3 NCs. The NdCl3-doped NCs exhibited blue emission at a peak wavelength of 478 nm with a high PLQY of 97% in solution. We found that the Nd3+ cation incorporated into the NCs more effectively suppressed nonradiative recombination compared with common halide anion exchange from temperature dependence of optical properties. Blue LEDs based on NdCl3-doped NCs had an external quantum efficiency of 2.7%, which represents a considerable performance improvement compared with LEDs based on organic chloride salt-doped NCs.

A highly luminescent mononuclear Al complex with β-diketone ligands exhibiting superior thermally activated delayed fluorescence (TADF) properties was developed in this work. The complex showed yellow emission with promising photofunctions, including a near-unity photoluminescence quantum yield (PLQY), a rapid radiative decay rate, and a short delayed fluorescence lifetime in the solid state. When applied in a solution-processed organic light-emitting device, an external quantum efficiency (EQE) exceeding 18% and a low turn-on voltage of 2.9 V at 1 cd/m2 were obtained, surpassing those of the corresponding β-diketone ligand. Metal complexation with Al generated unique electronic structures that significantly strengthened the photofunctions of the original β-diketone ligand in the solid state.

Metal halide perovskite nanocrystals (NCs) have been considered promising materials for applications in light-emitting diodes (LEDs) because of their excellent optoelectronic properties. Inkjet printing is a promising solutionprocessed technique for perovskite NC LEDs because of the possibilities of using drop on-demand printing with efficient ink utilization. However, perovskite NCs are thermally unstable, which can cause irreversible phase transitions and optical quenching under high-temperature annealing conditions. Here, we demonstrate an inkjet-printed CsPbBr 3 NC film for the fabrication of LEDs using high-boiling decalin and octane mixed solvents. The inkjet-printed CsPbBr 3 NC film exhibited a high photoluminescence quantum yield (PLQY) of 61.8% and retained its crystal structure even after high-temperature annealing at 200 °C, whereas the spin-coated CsPbBr 3 NC films showed a decrease in PLQY from 67.3% to 30.6%. The inkjetprinted CsPbBr 3 NC LED with a bank-free structure and large-area coating process exhibited a maximum luminance of 1890 cd m −2 and a peak external quantum efficiency of 5.9%, which is a 6-fold higher efficiency than those of spin-coated CsPbBr 3 NC LEDs with a high-temperature annealing process.

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The synthesis of 3‐(phenylcarbonyl)‐1H‐indazole derivatives via the intramolecular cyclization of triazene derivatives substituted by a 2‐(phenylethynyl)phenyl group at the position 3 was developed. The azonium salt, the key intermediate in the reaction, was prepared under mild conditions from trimethylsilyl iodide (TMSI) obtained from an in situ mixture of trimethylsilyl chloride (TMSCl) and sodium iodide (NaI). The obtained 3‐(phenylcarbonyl)‐1H‐indazole derivatives exhibited interesting optical properties including phosphorescence, which was verified by theoretical calculations.