Halide exchange and surface modification of metal halide perovskite nanocrystals with alkyltrichlorosilanes

Solution mediated halide exchange engineering for the fabrication of a thick CsPbCl3 film and its application in photovoltaics with outstanding performance

It is a big challenge to prepare thick CsPbCl3 films using traditional solution processed approaches owing to the low solubility of precursors of PbCl2 and CsCl in common solvents. Here, we propose an indirect solution process to prepare thick CsPbCl3 films. In this new approach, a mother film of CsPbBr3 is first prepared through a solution process, and then it is dipped into a diluted HCl/methanol solution. During the dipping process, it triggers a halide exchange reaction between Br- and Cl-, and it eventually produces a thick CsPbCl3 film (∼400 nm) with high quality and purity. Afterwards, a carbon based hole transportation layer (HTL) free solar cell with a configuration of FTO/TiO2/CsPbCl3/carbon is constructed, and it delivers an average PCE of 1.23% and an outstanding PCE of 1.39% in a batch of PSCs. Meanwhile, the solar cell maintains its 82% initial PCE after storage in open air for 31 days. This work overcomes the obstacle of the traditional solution approach for the preparation of CsPbCl3 films, which makes it promising for preparing various CsPbCl3 film-based devices via a solution process.

Improved Long-Term Reliability of a Silica-Encapsulated Perovskite Quantum-Dot Light-Emitting Device with an Optically Pumped Remote Film Package

In this study, inorganic perovskite (CsPbBr₃) quantum dots are wrapped in SiO₂ to provide better performance against external erosion. Long-term storage (250 days) is demonstrated with very little changes in the illumination capability of these quantum dots. While in the continuous aging procedure, different package architectures can achieve very different lifetimes. As long as 6000 h of lifetime can be expected from these quantum dots, but the blue shift of emission wavelength still needs more investigation.

Emission wavelength control of CsPb(Br1−xClx)3 nanocrystals for blue light-emitting diode applications

A facile synthetic method of CsPb(Br_1−xCl_x)₃ halide perovskite nanocrystals, which emit light with the wavelengths ranging from green to blue based on an anion exchanging reaction using a halide exchange additive was reported.

Fast, tunable and reversible anion-exchange in CsPbBr3 perovskite nanocrystals with hydrohalic acids

Anion-exchange with metal chloride salts in CsPbBr₃ perovskite nanocrystals.

Ligand-Mediated Release of Halides for Color Tuning of Perovskite Nanocrystals with Enhanced Stability

The rich chemistry of metal halide perovskites has enabled various methods of band structure control and surface passivation. Here we report a highly facile and efficient post-treatment approach for precise color tuning of cesium lead halide perovskite nanocrystals (NCs) with enhanced stability. By utilizing a special multifunctional organic ligand, triphenyl(9-phenyl-9H-carbazol-3-yl)phosphonium bromide (TPP-Carz), carbon-halide bond cleavage can be achieved to release halide ions from halogenated solvents in a controlled manner for color tuning of perovskite NCs via ion exchange. Besides controlled release of halide ions for anion exchange, TPP-Carz can effectively passivate the surfaces of perovskite NCs simultaneously. As a result, perovskite NCs prepared by this post-treatment method with tunable colors over the entire visible spectrum have shown significantly improved luminescence and stability in comparison to the ones prepared using reactive anion precursors without surface passivation by TPP-Carz.

Tuning from Quantum Dots to Magic Sized Clusters of CsPbBr3 Using Novel Planar Ligands Based on the Trivalent Nitrate Coordination Complex

We report the first demonstration of using trivalent metal hydrated nitrate coordination complexes (TMHNCCs) as novel passivation ligands to control the synthesis of magic sized clusters (MSCs) and quantum dots (QDs) of CsPbBr₃ perovskite at room temperature. We can easily tune from QDs to MSCs or produce a mixture of the two by changing the amount of TMHNCC ligands used, with more ligands favoring MSCs. The original TMHNCC introduced, aluminum nitrate nonahydrate [ANN, Al(NO₃)₃·9H₂O], led to the production of aluminum dihydroxide nitrate tetrahydrate {ADNT, [Al(OH)₂(NO₃)]·4H₂O}, with the assistance of oleic acid (OA) and oleylamine (OAm). Through several control experiments, we determined that ADNT is the primary ligand for effectively passivating the MSCs and QDs, with OAm being essential for deprotonating ANN and OA for adjusting the pH of the reaction system. We suggest that ADNT is planar on the surface of the MSCs or QDs with its NO₃^- and OH^- groups binding to the Cs⁺ and Pb²⁺ defect sites and Al³⁺ binding to the Br^- defect sites of the MSCs or QDs.