(202d) High-Temperature Flow Synthesis of Lead Halide Perovskite Nanocrystals

Since their discovery in 2015, all-inorganic lead halide perovskite (LHP) nanocrystals (NCs) have proven an excellent candidate to outperform conventional II-VI semiconductor NCs. [1] The facile and broad emission tunability of LHP NCs coupled with their narrow emission linewidth and high quantum yield make them an ideal candidate for next-generation printed energy technologies.

The most commonly used approach for discovery, fundamental studies, and development of LHP NCs is through conventional batch methods (e.g., round-bottom flasks). [2] Despite the ease of setup assembly, the batch reactors are suffering from limited heat and mass transport rates, absence of appropriate in situ materials characterization probes, batch-to-batch variations, and high reagents consumption. Recently, microfluidic platforms have gained significant interest for continuous manufacturing and precision synthesis of complex nanomaterials.[2] The reduced active reactor volume of microreactors compared to batch reactors allows for reliable nanomaterial synthesis and characterization with intensified transport phenomena, integration of in situ spectral monitoring probes, facile process automation, and reduced reagent consumption and waster generation. [2] These unique attributes make microfluidic platforms a highly effective tool for accelerated synthesis, optimization, and fundamental formation mechanism studies of high-quality LHP NCs. Despite the pioneering work in synthesis of LHP NCs, their formation mechanism using the widely adopted high-temperature synthetic route is not well-understood, thereby limiting the large scale production of LHP NCs for adoption by emerging printed energy technologies. [3]

In this work, we present, a modular and reconfigurable flow synthesis platform to study and unveil the formation mechanism of LHP NCs via one-pot high-temperature synthetic route. The unique modular design of the developed microfluidic platform allows access to three high-temperature synthetic routes of LHP NCs, including heat-up, hot-injection. Next, we utilized the developed flow synthesis platform to deconvolute the effects of interdependent reaction parameters controlling the NC morphology (nanocube vs. nanoplatelet) and optical properties of a model LHP NCs, cesium lead iodide (CsPbI₃). The results of the in-flow high-temperature synthesis of CsPbI₃ NCs, unveiled a change in the NC formation mechanism at temperatures higher than 150°C, manifested by the observed change in the NC morphology. Additionally, capitalizing on the excellent heat and mass transfer rates offered by microreactors, we demonstrated the unique capability of flow reactors for scalable production of high-quality CsPbI₃ NCs, independent of the target product volume.

The developed modular flow chemistry technology unveiled in this work provides a new frontier for high-temperature studies of solution-processed LHP NCs and enables their consistent and reliable continuous nanomanufacturing for next-generation energy technologies.

References:

[1] Abdel-Latif, K.; Bateni, F.; Crouse, S.; Abolhasani, M. Flow Synthesis of Metal Halide Perovskite Quantum Dots: From Rapid Parameter Space Mapping to AI-Guided Modular Manufacturing. Matter 2020, 3 (4), 1053–1086. https://doi.org/10.1016/j.matt.2020.07.024.

[2] Abdel‐Latif, K.; Epps, R. W.; Kerr, C. B.; Papa, C. M.; Castellano, F. N.; Abolhasani, M. Facile Room‐Temperature Anion Exchange Reactions of Inorganic Perovskite Quantum Dots Enabled by a Modular Microfluidic Platform. Adv. Funct. Mater. 2019, 29 (23), 1900712. https://doi.org/10.1002/adfm.201900712.

[3] Antami, K.; Bateni, F.; Ramezani, M.; Hauke, C. E.; Castellano, F. N.; Abolhasani, M. CsPbI ₃ Nanocrystals Go with the Flow: From Formation Mechanism to Continuous Nanomanufacturing. Adv Funct Materials 2021, 2108687. https://doi.org/10.1002/adfm.202108687.