Lead halides perovskites nanocrystal synthesized in green solvents

Description

Lead halides perovskites nanocrystals (LHPs NCs) are an important class of materials currently widely studied due to their physical properties such as high electron mobility, low trap density, tunable and high emission. The optoelectronic properties of the LHPs NC depends on the quantum confinement of the nanocrystal; for example, a lowering in the crystal dimension enhances the energy emission. One of the most used synthetic strategies is the Hot Injection Method (HInj) that allows a precise control over size and morphologies, reflected in a control of the optoelectronic properties of the final material. Briefly, HInj involves the rapid injection of the precursor (e.g. Cs+ salt) into a solution of an non-polar solvent with high boiling point in presence of the other precursors (e.g. PbX2 salt) and one or more organic ligands (alkyl carboxylic acid and amine), under inert atmosphere and at a temperature generally between 140°C and 200°C. The reaction starts immediately with a nucleation of the crystal and continues according to the desired final product and the interaction between the elements. Unfortunately, HInj is performed in solvent as octadecene (ODE), dioctyl ether, diphenyl ether etc. Yet, some vegetable terpenes, as Limonene or α-pinene, have good characteristics, in terms of dielectric constant and boiling point, to be a potential substitute of the aforementioned solvent in NCs synthesis. Here, we report the optimization of the synthesis of LHPs using green solvents. All the tests have been chosen according to a Plackett–Burman experimental design; through a following multivariate optimization, it would be possible to obtain the best conditions in terms of injection temperature, solvent type, amount of starting material and nanocrystal's growth time to have the product with a photoluminescence quantum yield and a shape control comparable to the traditional syntheses.

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