All-inorganic perovskite quantum dots (QDs) have emerged as potentially promising materials for lighting and displays, but their poor thermal stability restricts their practical application. In addition, optical characteristics of the blue-emitting CsPbX3 QDs lag behind their red- and green-emitting counterparts. Herein, we addressed these two issues by doping divalent Cu2+ ions into the perovskite lattice to form CsPb1–x Cu x X3 QDs. Extended X-ray absorption fine structure (EXAFS) measurements reveal that doping smaller Cu2+ guest ions induces a lattice contraction and eliminates halide vacancies, which leads to an increased lattice formation energy and improved short-range order of the doped perovskite QDs. This results in the improvement of both the thermal stability and the optical performance of CsPb1–x Cu x (Br/Cl)3 QDs, which exhibit bright blue photoluminescence at 450–460 nm, with a high quantum yield of over 80%. The CsPb1–x Cu x X3 QD films maintain stable luminescence performance even when annealed at temperatures of over 250 °C.

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.

A surface engineering strategy aimed at improving the stability of CsPbI 3 perovskite quantum dots (QDs) both in solution and as films is demonstrated, by performing partial ligand exchange with a short chain ligand, 2-aminoethanethiol (AET), in place of the original long chain ligands, oleic acid (OA) and oleylamine (OAm), used in synthesis. This results in the formation of a compact ligand barrier around the particles, which prevents penetration of water molecules and thus degradation of the films and, in addition, at the same time improves carrier mobility. Moreover, the AET ligand can passivate surface traps of the QDs, leading to an enhanced photoluminescence (PL) efficiency. As a result, AET-CsPbI 3 QDs maintain their optical performance both in solution and as films, retaining more than 95% of the initial PL intensity in water after 1 h, and under ultraviolet irradiation for 2 h. Photodetectors based on the AET-CsPbI 3 QD films exhibit remarkable performance, such as high photoresponsivity (105 mA W −1 ) and detectivity (5 × 10 13 Jones at 450 nm and 3 × 10 13 Jones at 700 nm) without an external bias. The photodetectors also show excellent stability, retaining more than 95% of the initial responsivity in ambient air for 40 h without any encapsulation.

All-inorganic perovskite cesium lead halide quantum dots (QDs) have been widely investigated as promising materials for optoelectronic application because of their outstanding photoluminescence (PL) properties and benefits from quantum effects. Although QDs with fullspectra visible emission have been synthesized for years, the PL quantum yield (PLQY) of pure blue-emitting QDs still stays at a low level, in contrast to their green-or redemitting counterparts. Herein, we obtained core−shell structured cubic CsPbBr 3 @amorphous CsPbBr x (A-CsPbBr x ) perovskite QDs via a facile hot injection method and centrifugation process. The core−shell structure QDs showed a record blue emission PLQY of 84%, which is much higher than that of blue-emitting cubic CsPbBr 3 QDs and CsPbBr x Cl 3−x QDs. Furthermore, a blue-emitting QDsassisted LED with bright pure blue emission was prepared and illustrated the core−shell QDs' promising prospect in optoelectrical application.

A fully automated spray-coated technology with ultrathin-film purification is exploited for the commercial large-scale solution-based processing of colloidal inorganic perovskite CsPbI 3 quantum dot (QD) films toward solar cells. This process is in the air outside the glove box. To further improve the performance of QD solar cells, the short-chain ligand of phenyltrimethylammonium bromide (PTABr) with a benzene group is introduced to partially substitute for the original long-chain ligands of the colloidal QD surface (namely PTABr-CsPbI 3 ). This process not only enhances the carrier charge mobility within the QD film due to shortening length between adjacent QDs, but also passivates the halide vacancy defects of QD by Br − from PTABr. The colloidal QD solar cells show a power conversion efficiency (PCE) of 11.2% with an open voltage of 1.11 V, a short current density of 14.4 mA cm −2 , and a fill factor of 0.70. Due to the hydrophobic surface chemistry of the PTABr-CsPbI 3 film, the solar cell can maintain 80% of the initial PCE in ambient conditions for one month without any encapsulation. Such a low-cost and efficient spraycoating technology also offers an avenue to the film fabrication of colloidal nanocrystals for electronic devices.with a large bandgap of 2.82 eV. [24,25] Many efforts have tried to partly replace I − with Br − to increase the stability of the black phase. [17,26,27] Unfortunately, the introduction of the bromine component enlarges the bandgap of the perovskite, correspondingly to harm the light-harvesting performance. The cubic structure of CsPbI 3 also can be stabilized by the colloidal quantum dot (QD) method, because the enlarging surface energy inhibits the phase transition. [28][29][30] In addition, on the basis of the multiple exciton generation effects, the narrow bandgap colloidal QDs will exceed the single-junction Shockley-Queisser solar efficiency limit to achieve higher theoretical efficiency. [31,32] Several efforts have built the devices with quite inspiring efficiency using the CsPbI 3 QD film as the active layer. [14,30,[33][34][35][36][37][38] However, the CsPbI 3 QDs are usually deposited to form the thin film by the spin-coating method. This method is an undesirable way to realize the scaled manufacture of the QD thin film because of the small deposition area. [39] To economize the cost of materials and realize scalable film deposition, the spray coating is emerging as a typical process for the fabrication of the thin films and has been used in the commercial paint coat technology. [32,39] However, the spray-coating process is hard to obtain high quality compact thin-film of colloidal QD due to long chain surface organic ligands of QD that weakens the adhesive force between QD and substrate. The surface ligands are obstructive to the formation of QD films and performance of the devices by hindering the charge transport. But the surface ligands are necessary to maintain monodisperse QDs and suppress their agglomeration. How to balance the surface ligands and the adhesive f...