Highly Soluble CsPbBr₃ Perovskite Quantum Dots for Solution-Processed Light-Emission Devices

Abstract

We report on the synthesis of CsPbBr 3 perovskite quantum dots (PeQDs) with a high solubility of 75 g/L in toluene and a good film-forming property, as enabled by a dense layer of didodecyldimethylammonium bromide and octanoic acid surface ligands. The crystalline and monodisperse PeQDs feature a cubic-like shape, with an edge length of 10.1 nm, and a high photoluminescence quantum yield of greater than 90% in toluene solution and 36% as a thin film. We find that the PeQDs are n-type doped following the synthesis but also that they can be p-type and additionally n-type doped by in situ electrochemistry. These combined properties render the PeQDs interesting for the emitter in solution-processed light-emitting electrochemical cells (LECs), and we report a PeQD-LEC with air-stabile electrodes that emits with a narrow emission spectrum (λ peak = 514 nm, full width at half-maximum = 24 nm) and a luminance of 250 cd/m 2 at 4 V and a luminance of 1090 cd/m 2 at 6.8 V. To reach this performance, it was critical to include a thin solution-processed layer comprising p-type poly(vinyl carbazole) and a tetrahexylammonium tetrafluoroborate ionic liquid between the PeQD emission layer and the anode in order to compensate for the as-synthesized n-type doping of the PeQDs.

Stable and Bright Electroluminescent Devices utilizing Emissive 0D Perovskite Nanocrystals Incorporated in a 3D CsPbBr3 Matrix

“…Alternative to these emissive PNCs, all the previous reports of 3D–0D composites or light‐emitting devices incorporating a non‐emissive 0D component involved changing the CsBr to PbBr 2 precursor ratio, where increasing the CsBr ratio led to more 0D phase formation, which in turn reduced the crystallite/grain size of the 3D part leading to increased confinement. [ 10b,14b,23 ] To compare our 3D–0D PNC blend with those from literature reports, we prepared composite films with an excess of CsBr (CsBr:PbBr 2 = 2:1 and 3:1) and analyzed the structural details and device performance relative to the 3D and 3D–0D (high PLQY) PNC composite. As can be seen from the scanning electron microscopy (SEM) images provided in Figure a, the introduction of 0D (high PLQY) PNCs reduces the grain size significantly compared to the 3D film (CsBr:PbBr 2 = 1.5:1).…”

“…With an increase in the CsBr:PbBr 2 ratio, the XRD shows an appearance and consecutive increase of characteristic 0D Cs 4 PbBr 6 peaks at 12.7° and 22.4° (marked red). [ 10b,23 ] The most intense 0D peaks were observed for CsBr:PbBr 2 ratio of 3:1, indicating an increased amount of 0D component in the composite. However, for the 3D–0D PNC blend, the ratio of 0D peaks relative to 3D remains negligible, which agrees with the presence of a low weight percentage of 0D PNCs relative to 3D.…”

Aromatic Carboxylic Acid Ligand Management for CsPbBr3 Quantum Dot Light-Emitting Solar Cells

“…CsPbBr 3 with a wide band gap ( E g ∼2.4 eV) generates a high open-circuit voltage ( V OC ) and has great potential for application in tandem solar cells as top cells. − Moreover, CsPbBr 3 QDs overcome the problem of phase instability and exhibit narrow emission linewidth and high photoluminescence quantum yield, showing huge potential in LEDs − and lasers. − A room-temperature method was reported to synthesize CsPbBr 3 nanocrystal inks, and the corresponding solar cells were fabricated, delivering an efficiency exceeding 5% and a V OC higher than 1.5 V . However, the CsPbBr 3 nanocrystals showed poor dispersibility in hexane solvent, which seriously hindered the film uniformity and the device reproducibility.…”

Facile generation of thenil and furil based blue emitters for the fabrication of non-doped and solution-processed light-emitting electrochemical cells

“…6,7 The emissive layer, which is the heart of LECs is mainly composed of emitting materials like conjugated polymers, ionic transition metal complexes, organic small molecules and perovskites. 8–21 However, the purification and polymer synthesis were troublesome, and the large-scale use of costly and rare transition metals was not always a realistic choice. 22,23 On the other hand, metal-free organic molecules showed excellent performance in OLEDs and this inspired the incorporation of organic SMs into LEC active materials due to their attractive features like a facile synthesis, and excellent chemical and thermal stabilities with good solubility in common organic solvents.…”