Alkyl-Thiol Ligand-Induced Shape- and Crystalline Phase-Controlled Synthesis of Stable Perovskite-Related CsPb₂Br₅ Nanocrystals at Room Temperature

Abstract

Controlled synthesis of colloidal all-inorganic lead halide perovskite semiconductor nanocrystals, such as CsPbBr, with tunable size, shape, composition, and crystalline phase have recently attracted wide interest for photonic and optoelectronic applications. Herein, we report a new strategy for using alkyl-thiols to induce the transformation of CsPbBr to perovskite-related cesium lead halide (CsPbBr) with controlled morphology and a crystalline phase at room temperature. By rational tuning the ratios of the alkyl-thiol ligands to alkyl-amines or to alkyl-acids, the as-synthesized colloidal nanocrystals can be rationally controlled from orthorhombic crystalline-phase CsPbBr to tetragonal-phase CsPbBr nanosheets and nanowires with high yield. Significantly, the tetragonal CsPbBr nanowires and nanosheets have high stability in high-temperature and high-humidity environments. These findings may open new directions for large-scale synthesis of shape- and crystalline phase-controlled perovskite nanocrystals for high-performance, low-cost optical electronic and optoelectronic devices.

Stability of Quantum Dots, Quantum Dot Films, and Quantum Dot Light‐Emitting Diodes for Display Applications

“…For example, CsPbBr 3 perovskite QDs with TDPA ligands maintained 75% of their initial PL intensity under water after 5 h, while bare CsPbBr 3 QDs maintained only 7% of their PL intensity after an hour . However, strong thiol ligands do not help to enhance the stability of perovskite QDs, because the thiol anchor groups destroy the crystallinity of the QDs due to the great binding force with lead halide . Thus, the PL intensity of perovskite QDs is drastically decreased by thiol ligands …”

Emergence of Nanoplatelet Light-Emitting Diodes

“…Particularly, the parasite of secondary phase CsPb 2 Br 5 nanoparticles on the cubic CsPbBr 3 nanocrystals can (i) improve current efficiency by lowering diffusion length of excitons; (ii) reduce the trap density in the bandgap; (iii) enhance the ionic conductivity by lowering the barrier against the electronic and ionic transport; (iv) enhance emission lifetime by reducing non-radiative energy transfer to trap states by controlling trap density, which is a key to the high performance. However, detailed EL as well as optical properties for single-component CsPb 2 Br 5 film was not reported [147,148,149,150]. …”

Zero-Dimensional Cesium Lead Halides: History, Properties, and Challenges

“…Various different optical properties have been reported, ranging from a nonluminescent wide indirect bandgap material 52,103−105 to a green material with strong green PL (again, around 515 nm). 22,106−109 …”