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Organic metal halide perovskites have rapidly emerged as among the leading candidates for the next generation of photovoltaic and light-emitting devices. The band gap, exciton binding energy, and absorption cross-section of these materials are tunable to some extent by compositional variation. Dimensional confinement represents an attractive alternative to compositional variation for tuning these properties via quantum confinement close to the Böhr radius. While the stabilization of few-layered nanoplatelets of methylammonium lead bromide has recently been demonstrated, mechanistic understanding of synthetic parameters resulting in dimensional confinement remains to be developed. Here we show that the layer thickness can be precisely modulated as a function of the chain length and concentration of the added alkylammonium cations. Surface capping ligands bind preferentially to sheets of corner sharing PbBr6 octahedra and thereby buffer the extent of supersaturation of monomeric units enabling precise modulation of the layer-by-layer growth of 2D nanoplatelets. Crystal growth can be confined to yield nanoplatelets with tunable unit cell thickness spanning between one and six layers, which allows for precise tuning of the emissive properties of 2D perovskite nanoplatelets in the range of 430-520 nm depending on the layer thickness. The results suggest a generalizable strategy for tuning the layer thickness of these materials as a function of the alkyl chain length of the ligands. [ABSTRACT FROM AUTHOR]

Thenucleation and growth behavior of Cu nanoparticles during thermalheating of Cu(II) complex inks for printed Cu metallization were investigated,particularly focusing on the effects of the amine concentration onthe microstructure evolution and electrical conductivity. Herein,the dual effects of hexylamine as a reducing agent dissociating thecarboxyl group from the precursor and a capping agent hindering thesubsequent growth of Cu nuclei were confirmed. On the basis of suchdual effects of amine, the sufficient complexation of the Cu(II) precursorwith a high amine concentration in the ink led to the single-routegrowth of Cu nanoparticles during thermal heating, which resultedin the dense film with a narrow particle size distribution exhibitinga high electrical conductivity. The electrical conductivity of thefilm could be further enhanced by a reducing atmosphere with formicacid. Significantly, the understanding of the ink chemistry and thenucleation and growth kinetics in the metal ion complex or metal–organicdecomposition (MOD) ink can provide the design rules for the formulationof the solution-type inks to control the microstructure of printedmetallization. [ABSTRACT FROM AUTHOR]