We report a versatile capillary-based droplet reactor for the controlled synthesis of nanoparticles over a wide range of flow conditions and temperatures. The reactor tolerates large flow-rate differentials between individual reagent streams, and allows droplet composition to be varied independently of residence time and volume. The reactor was successfully applied to the synthesis of metal (Ag), metal-oxide (TiO(2)) and compound semiconductor (CdSe) nanoparticles, and in each case exhibited stable droplet flow over many hours of operation without fouling, even for reactions involving solid intermediates. For CdSe formed by the reaction of Cd oleate and Se, highly controlled growth could be achieved at temperatures of up to 250 °C, with emission spectra varying smoothly and reproducibly with temperature and flow-rate. The droplet reactor showed exceptional stability when operated under constant flow-rate and temperature conditions, yielding particles with well-defined band-edge emission spectra that did not vary over the course of a full day's continuous operation.
Rapid extraction of photogenerated charge carriers is essential to achieve high efficiencies with perovskite solar cells (PSCs). Here, a new mesoscopic architecture as electron‐selective contact for PSCs featuring 40 nm sized TiO2 beads endowed with mesopores of a few nanometer diameters is introduced. The bimodal pore distribution inherent to these films produces a very large contact area of 200 m2 g−1 whose access by the perovskite light absorber is facilitated by the interstitial voids between the particles. Modification of the TiO2 surface by CsBr further strengthens its interaction with the perovskite. As a result, photogenerated electrons are extracted rapidly producing a very high fill factor of close to 80% a VOC of 1.14 V and a PCE up to 21% with negligible hysteresis.
We report a multichannel microfluidic droplet reactor for the large-scale, high temperature synthesis of nanocrystals. The reactor was applied here to the production of CdTe, CdSe and alloyed CdSeTe nanocrystals, and found in all cases to provide high quality quantum dots with spectral properties that did not vary between channels or over time. One hour test runs yielded 3.7, 1.5 and 2.1 g of purified CdTe, CdSe and the alloy, respectively, using 0.4 M cadmium precursor solutions and carrier and reagent phase flow rates of 4 and 2 ml min À1. A further nine hour test-run applied to CdTe, utilizing increased carrier and reagent flow rates of 5 and 3 ml min À1 , yielded 54.4 g of dry purified material, corresponding to a production rate of 145 g per day. The reactor architecture is inherently scalable and, with only minimal modifications, should allow for straightforward expansion to the kilogram-per-day production levels sought by industry.
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