On-and-off feedback control with hysteresis algorithm for automatic flow chemistry synthesis of the desired MAPbBrXI3-X quantum dot

Abstract

Recent advances in the development of hybrid organic–inorganic halide perovskite quantum dots (HP-QDs) have proven their versatility and potential applications in photovoltaics and light sources through compositional tuning. However, the compositional complexity for mixed-cation and/or mixed-halide HP-QDs would require repetitive optimization processes to obtain the desired perovskite crystals via traditional batch-scale chemistry, causing prolonged time, labor, and cost. To address this issue, we herein report a dynamic flow chemistry synthetic system operated with the on-and-off feedback control with hysteresis algorithm to produce methylammonium lead trihalide perovskite quantum dots (MAPbBrXI3-X QDs with 0 ≤ X ≤ 3), automatically showing a target emission wavelength. We set up the target photoluminescent (PL) emission wavelength of the MAPbBrXI3-X QDs and started with an arbitrary flow rate of the bromide and iodide precursor solution. The PL emission wavelength of the synthesized perovskites was in-situ monitored in the flow cell equipped with a miniaturized optical detector. By comparing the measured wavelength with the target one, the controlling algorithm recalculated to adjust the flow rates of the bromide and iodide precursor solution accordingly. Then, the PL emission wavelength of the newly synthesized MAPbBrXI3-X QDs was detected again in real-time, and the iterative feedback control process was repeated until the observed wavelength was matched with the user-defined emission target. Thus, the desired MAPbBrXI3-X QDs could be obtained eventually through the feedback control in an automatic manner, suggesting an advanced flow chemistry synthetic platform to produce on-demanded nanomaterials with high efficiency.