High Throughput Screening Platform for Cesium-Lead Perovskite Nanocrystal Synthesis

Colloidal organic/inorganic perovskites have great potential as photoactive compounds in solar cells and light emitting diodes. Scale-up of perovskite nanomanufacturing will require methods to precisely tune perovskite properties. The recent advent of colloidal synthesis in flow offers a promising method for controlling synthesis conditions (residence time, mixing, temperature, pressure, etc). In turn, synthesis in flow enables the creation of uniform nanoparticles with tunable band gap, photoluminescence, and crystal structure. This poster presents a novel modular microfluidic reactor platform for the rapid and automated synthesis of highly photoluminescent cesium lead perovskite nanocrystals at room-temperature. A fiber-optic UV spectrometer and orthogonal light sources (for fluorescence and absorption) are connected to a translational flow cell to capture spectra at varying residence times (while maintaining flow rates and mixing constant). Furthermore, the reactor platform is connected to a LabView script, which enables testing of a large parameter space in a short amount of time (up to 30,000 spectra per day). The script utilizes an automatic alignment algorithm to ensure the translational stage is accurately aligned with the 20 sampling ports along the reactor.

Using the platform, the kinetics of the CsPbBr₃ synthesis reaction are elucidated at timescales as early as 200 ms in single- and multi-phase regimes. In multi-phase experiments at low flow rates, a local variance algorithm is applied to solely capture spectra of individual liquid plugs. It is shown that increasing flow rate at a constant residence time results in greater blue-shifts of emission wavelength for multi-phase systems than single-phase systems, indicating that the nucleation and growth kinetics of cesium-lead perovskite reactions are highly dependent on mass transfer. Furthermore, the demonstrated microfluidic approach offers greater control over mass transfer across different scales than batch methods, which results in perovskite nanocrystals with uniform properties. This reactor platform represents an important step to developing scalable methods for continuous nanomanufacturing of perovskites for photoactive applications.