Facile Droplet-based Microfluidic Synthesis of Monodisperse IV-VI Semiconductor Nanocrystals with Coupled In-Line NIR Fluorescence Detection

Abstract

We describe the realization of a droplet-based microfluidic platform for the controlled and reproducible synthesis of lead chalcogenide (PbS, PbSe) nanocrystal quantum dots (QDs). Monodisperse nanocrystals were synthesized over a wide range of experimental conditions, with real-time assessment and fine-tuning of material properties being achieved using NIR fluorescence spectroscopy. Importantly, we show for the first time that real-time monitoring of the synthetic process allows for rapid optimization of reaction conditions and the synthesis of high quality PbS nanocrystals, emitting in the range of 765–1600 nm, without any post-synthetic processing. The segmented-flow capillary reactor exhibits stable droplet generation and reproducible synthesis of PbS nanocrystals with high photoluminescence quantum yields (28%) over extended periods of time (3–6 h). Furthermore, the produced NIR-emitting nanoparticles were successfully used in the fabrication of Schottky solar cells, exhibiting a power conversion efficiency of 3.4% under simulated AM 1.5 illumination. Finally, the droplet-based microfluidic platform was used to synthesize PbSe nanocrystals having photoluminescence peaks in the range of 860–1600 nm, showing the exceptional control and stability of the reactor.