The research on metal halide perovskite light‐emitting diodes (PeLEDs) with green and infrared emission has demonstrated significant progress in achieving higher functional performance. However, the realization of stable pure‐blue (≈470 nm wavelength) PeLEDs with increased brightness and efficiency still constitutes a considerable challenge. Here, a novel acid etching‐driven ligand exchange strategy is devised for achieving pure‐blue emitting small‐sized (≈4 nm) CsPbBr3 perovskite quantum dots (QDs) with ultralow trap density and excellent stability. The acid, hydrogen bromide (HBr), is employed to etch imperfect [PbBr6]4− octahedrons, thereby removing surface defects and excessive carboxylate ligands. Subsequently, didodecylamine and phenethylamine are successively introduced to bond the residual uncoordinated sites of the QDs and attain in situ exchange with the original long‐chain organic ligands, resulting in near‐unity quantum yield (97%) and remarkable stability. The QD‐based PeLEDs exhibit pure‐blue electroluminescence at 470 nm (corresponding to the Commission Internationale del'Eclairage (CIE) (0.13, 0.11) coordinates), an external quantum efficiency of 4.7%, and a remarkable luminance of 3850 cd m−2, which is the highest brightness reported so far for pure‐blue PeLEDs. Furthermore, the PeLEDs exhibit robust durability, with a half‐lifetime exceeding 12 h under continuous operation, representing a record performance value for blue PeLEDs.

Bright red emission (620-650 nm) from perovskite light-emitting diodes (PeLEDs) is usually achieved via a composition including both bromine and iodine anions, which results in poor performance and stability due to phase separation under operating conditions. Here a large-scale ligand-assisted reprecipitation method is devised with nonpolar solvent that enables the fabrication of CsPbI 3 nanowire clusters, emitting at 600 nm. The blue-shift of this emission relative to that of bulk CsPbI 3 (≈700 nm) is attributed to quantum confinement in nanowires. The growth of the nanowires is along the [011] crystal direction and is vacancy driven, resulting in the healing of surface defects and thereby a high photoluminescence quantum yield of 91%. The clusters with ultralow trap density show remarkable structural and environmental stability. PeLEDs based on these clusters exhibit an external quantum efficiency of 6.2% with Commission Internationale de l'Eclairage coordinates of (0.66, 0.34), and record luminance of 13 644 cd m −2 of red electroluminescence. The half-lifetime under an accelerated stability test is 13.5 min for an unencapsulated device in ambient conditions operating at an initial luminance of 11 500 cd m −2 , which corresponds to an estimated half-lifetime of 694 h at 100 cd m −2 based on acceleration factor obtained by experimental testing.

In article number 2006722, Jianjun Tian and co‐workers report pure‐blue perovskite light‐emitting diodes (LEDs) based on ultralow‐trap‐density and extremely stable small‐sized CsPbBr3 quantum dots, which is achieved by a novel acid‐etching‐driven ligand exchange. The LEDs exhibit electroluminescence at 470 nm wavelength with external quantum efficiency of 4.7%, remarkable high luminance (3850 cd m−2), and long‐term operational stability T50 of 12 h.

Asphaltene can exist in both the dispersed state and the aggregated state in crude oil. Because of the changes in crude oil composition, pressure, or temperature, the asphaltene transition from dispersed asphaltene to aggregated asphaltene will occur and then influence the wax crystallization, gelation, and flow behavior of crude oil. In this paper, the asphaltene transition was realized by mixing two different crude oils for different times. The aggregated asphaltene was characterized by the optical microscopy and centrifugation-based separation method. The effects of asphaltene transition on wax crystallization, gelation, and flow behavior of crude oil were investigated by differential scanning calorimetry and rheological measurements. The results show that the aggregated asphaltene can serve as a crystal nucleus for wax molecules, promoting the wax precipitation, weakening the strength of the network of wax crystals, and delaying the gelation process of crude oil. On the other hand, the dispersed asphaltene can serve as the connecting point between wax crystals, accelerating the gelation of crude oil, and increasing the gel strength. The viscosity measurements below the wax appearance temperature show that the viscosity of crude oil increases because of the interaction between aggregated asphaltene and wax.

It is a big challenge to achieve pure-blue (≤470 nm) perovskite light-emitting diodes (PeLEDs) with high efficiency and stability. Here, we report pure-blue (electroluminescence at 469 nm) PeLEDs with a full width at halfmaximum of 21 nm, high external quantum efficiency of 10.3%, luminance of 12 060 cd m −2 , and continuous operation half-life of 25 h, representing the stateof-the-art performance. This design is based on strongly quantum confined CsPbBr 3 quantum dots (QDs) with suppression of Auger recombination, which was enabled by inorganic ligands, replacing initial organic ligands on the QDs. The inorganic ligand acts as a "capacitor" to alleviate the charge accumulation and reduce the exciton binding energy of the QDs, which suppresses the Auger recombination, resulting in much lower efficiency roll-off of PeLEDs. Thus, the devices maintain high efficiency (>10%) at high luminance (>2000 cd m −2 ), which is of considerable significance for the display application.