Quantum‐Confined Dodecahedron CsPbBr₃ Quantum Dots by A Sequential Post‐Treatment Strategy for Efficient Blue PeLEDs

Abstract

CsPbBr3 quantum dots (QDs) prepared through traditional hot‐injection and room temperature reprecipitation methods are usually hexahedral (nanoplate/cube) and green‐emitting. These methods severely obstruct the development of blue perovskite‐based light‐emitting diodes (PeLEDs) because the resultant QDs always suffer unachievable morphology regulation. Here, highly efficient blue‐emitting rhombic dodecahedron CsPbBr3 QDs (CsPbBr3 <12> QDs) are obtained by regulating morphological transformation for the first time through a novel and facile sequential post‐treatment strategy. Hydrobromide (‐NH3+) with stronger adsorption energy promotes the morphology transform of QDs from nanoplate to cube by substituting oleylamine in the first step. Then, polar solvent vapor eliminates PbX64− and led to the (112) crystal plane of the cube QDs being exposed, which is effectively stabilized by ‐NH3+ to realize morphology transition from cube to the dodecahedron. Highly efficient 12‐faceted dodecahedrons are endowed with significantly enhanced photoluminescence quantum yield of 89.8% at 476 nm as well as uniform size distribution and mono‐dispersity. The target blue PeLEDs achieve the maximum external quantum efficiency of 6.6% (480 nm) and excellent spectrum stability. This study provides a new strategy to prepare blue‐emitting CsPbBr3 <12> QDs by delicate control toward the growth and polyhedron process of crystal.

Tailoring Phase Distribution of Quasi‐2D Perovskites via Taurine‐Assistance Enables Efficient Blue Light‐Emitting Diodes

“…where N t , 𝜖 0 , 𝜖 r , V TFL , q, and L represent the defect density, vacuum capacitance, relative dielectric constant, starting voltage of the trap filling limit curve, elementary charge, and the thickness of perovskite film, respectively. [27] Based on dark current-voltage measurement (Figures S7 and S8, Supporting Information), the defect state density of TAU-added perovskite film is calculated to be 8.41 × 10 18 , which is significantly lower than that of the pristine film (9.95 × 10 18 ). The decreased defect state density verifies the above-mentioned conclusion.…”

Electron Transfer from an Optically Pumped Polyhedral Perovskite Nanocrystal to Pristine Fullerene

“…The obtained precipitation containing PNCs was redispersed in hexane and used for further optical studies and characterizations. Our 12-faceted PNCs are bright and characterized by a photoluminescence quantum yield (PLQY) of ∼81%. , …”

“…Synthesis of 12-faceted dodecahedron CsPbBr 3 PNCs involves the following two steps. 4,5 Step 1: Approximately 21.7 mg of cesium carbonate (Cs 2 CO 3 , ∼99%) was added to a solution of ∼1 mL of octadecene (ODE, technical grade, ∼90%) and ∼0.12 mL of oleic acid (OA, technical grade, ∼90%) and thoroughly mixed in a small round-bottom flask (RB), dried (at ∼120 °C) under a vacuum for half an hour, and then transferred to a N 2 environment for a complete dissolution of Cs 2 CO 3 after being converted to cesium-oleate by ∼1 h heating at high temperature. The obtained cesium-oleate precipitates out of the solution at room temperature, which was dissolved by heating before using it in the second step.…”

“…The obtained cesium-oleate precipitates out of the solution at room temperature, which was dissolved by heating before using it in the second step. 4,5 Step 2: In a separate RB, ∼45 mg of PbO (∼99%), ∼1 mL of OLm, ∼1 mL of OA, ∼5 mL of ODE (predried), and ∼120 mg of phenacyl bromide (∼98%) were thoroughly mixed and kept under vacuum for a long time (>1 h) and then transferred to a N 2 environment at high temperature (∼130 °C) to dissolve the solid particles. Afterward, the temperature of the clear solution was raised to ∼222 °C and the heating continued for 1 h. Next, ∼1/2 mL of the previously prepared cesium-oleate solution was added, annealed for ∼20 min, and quenched in an ice bath.…”

“…Our 12-faceted PNCs are bright and characterized by a photoluminescence quantum yield (PLQY) of ∼81%. 4,5 Sample Characterization. The HRTEM image confirms the dodecahedron morphology of our PNCs, resembling previous reports.…”