Solution Synthesis Approach to Colloidal Cesium Lead Halide Perovskite Nanoplatelets with Monolayer-Level Thickness Control

Abstract

We report a colloidal synthesis approach to CsPbBr3 nanoplatelets (NPLs). The nucleation and growth of the platelets, which takes place at room temperature, is triggered by the injection of acetone in a mixture of precursors that would remain unreactive otherwise. The low growth temperature enables the control of the plate thickness, which can be precisely tuned from 3 to 5 monolayers. The strong two-dimensional confinement of the carriers at such small vertical sizes is responsible for a narrow PL, strong excitonic absorption, and a blue shift of the optical band gap by more than 0.47 eV compared to that of bulk CsPbBr3. We also show that the composition of the NPLs can be varied all the way to CsPbBr3 or CsPbI3 by anion exchange, with preservation of the size and shape of the starting particles. The blue fluorescent CsPbCl3 NPLs represent a new member of the scarcely populated group of blue-emitting colloidal nanocrystals. The exciton dynamics were found to be independent of the extent of 2D confinement in these platelets, and this was supported by band structure calculations.

Colloidal lead halide perovskite nanocrystals: synthesis, optical properties and applications

“…They showed that the thickness of CsPbBr 3 nanoplatelets can be tuned from 1 to 5 unit cells thick by changing the reaction temperature, with the monolayer platelets emitting at 400 nm (Figure 6e), whereas the bulk-like crystals emitted at 520 nm (Figure 6d). Similarly, Manna and colleagues 65 have shown that the thickness of CsPbBr 3 platelets could be precisely tuned between 3 and 5 monolayers, keeping a narrow emission and a strong blue shift of the PL peak compared with that of bulk CsPbBr 3 . In addition, they have also shown that the lateral size of the quantum-confined CsPbBr 3 nanoplatelets (thickness~3 nm) can be controlled up to the micrometer range by varying the ratio of shorter ligands (octanoic acid and octylamine) to longer ligands (oleic acid and oleylamine), while maintaining their thickness and, to a large degree, the optical properties.…”

“…In a recent report Li et al 64 Figure 5 showed that CsPbX 3 NCs can be synthesized at room temperature, similar to the LARP method used for the MAPbX 3 system. Manna and colleagues 65 have demonstrated the synthesis of quantum-confined CsPbBr 3 nanoplatelets at room temperature. They have shown that anisotropic growth leads to the formation of nanoplatelets at room temperature through the injection of acetone in a mixture of precursor.…”

All-Inorganic Perovskite CsPb2Br5 Microsheets for Photodetector Application

“…To date, all-inorganic cesium lead halide perovskite have generated considerable attention because of their higher stability and outstanding optoelectronic properties comparable to the hybrid organic-inorganic perovskites [17][18][19][20]. Thus, a large number of CsPbX 3 (X = I, Br, Cl) perovskite nanostructures such as nanocrystals [21], nanowires [22], microsheets [23,24], nanocubes, were prepared by solution processing approach. Furthermore, the physical properties of all-inorganic nanocrystals could be adjusted by their geometric shape and size [25].…”

Strategy to overcome recombination limited photocurrent generation in CsPbX3 nanocrystal arrays

“…We further cross-checked that the method used to make the thin film conductive and photoconductive is not limited to this particular halide content. In particular, we demonstrated that the method can be applied to other shapes, including nanocubes (0D objects) and nanoplatelets 28 (2D objects, NPL) (see Figure S9), and to other Br:I ratios (see Figure S10). The typical responsivity of the film spans from 200 µA.W -1 to 1 mA.W -1 depending on the incident power.…”