Synthesis of Cs ₃ Cu ₂ I ₅ Nanocrystals in a Continuous Flow System

Abstract Achieving the goal of generating all of the world's energy via renewable sources and significantly reducing the energy usage will require the development of novel, abundant, nontoxic energy conversion materials. Here, a cost‐efficient and scalable continuous flow synthesis of Cs ₃ Cu ₂ I ₅ nanocrystals is developed as a basis for the rapid advancement of novel nanomaterials. Ideal precursor solutions are obtained through a novel batch synthesis, whose product served as a benchmark for the subsequent flow synthesis. Realizing this setup enabled a reproducible fabrication of Cs ₃ Cu ₂ I ₅ nanocrystals. The effect of volumetric flow rate and temperature on the final product's morphology and optical properties are determined, obtaining 21% quantum yield with the optimal configuration. Consequently, the size and morphology of the nanocrystals can be tuned with far more precision and in a much broader range than previously achievable. The flow setup is readily applicable to other relevant nanomaterials. It should enable a rapid determination of a material's potential and subsequently optimize its desired properties for renewable energy generation or efficient optoelectronics.