Alternative green solvents for the synthesis of perovskite nanocrystals

The rapid spread of nanotechnology calls for a search for alternative processes that can reduce negative impacts, both from an environmental and economical point of view, of the syntheses employed to obtain nanocrystals (NCs). Perovskite NCs are commonly synthesized in 1-octadecene (ODE), a molecule derivate from petroleum with certain drawbacks, such as polymerization during synthesis as well as difficulty in removal from the final NCs.

In our work, we exploited hot-injection methods to obtain perovskite NCs with different morphologies and stoichiometries by substituting the classical solvent with green molecules, i.e., limonene and pinene. Firstly, we demonstrated the possibility to obtain both lead and lead-free halide perovskites in different sizes and morphologies, retaining the optical properties of the same NCs prepared in ODE. Then, exploiting the relative high volatility of the green solvent, we demonstrated the possibility to recover—from the waste of the reactions—the pure molecules that can be reused for subsequent syntheses. Moreover, the NCs can be washed from the solvents using a vacuum pump, avoiding several washing steps.

In conclusion, green solvents can be employed in nanocrystal synthesis both to reduce the environmental impact of the process and to obtain “clean” particles while avoiding several washing steps, thereby preventing their degradation.