title: Automated synthesis of photovoltaic-quality colloidal quantum dots using separate nucleation and growth stages.
abstract: As colloidal quantum dot (CQD) optoelectronic devices continue to improve, interest grows in the scaled-up and automated synthesis of high-quality materials. Unfortunately, all reports of record-performance CQD photovoltaics have been based on small-scale batch syntheses. Here we report a strategy for flow reactor synthesis of PbS CQDs and prove that it leads to solar cells having performance similar to that of comparable batch-synthesized nanoparticles. Specifically, we find that, only when using a dual-temperature-stage flow reactor synthesis reported herein, are the CQDs of sufficient quality to achieve high performance. We use a kinetic model to explain and optimize the nucleation and growth processes in the reactor. Compared to conventional single-stage flow-synthesized CQDs, we achieve superior quality nanocrystals via the optimized dual-stage reactor, with high photoluminescence quantum yield (50%) and narrow full width-half-maximum. The dual-stage flow reactor approach, with its versatility and rapid screening of multiple parameters, combined with its efficient materials utilization, offers an attractive path to automated synthesis of CQDs for photovoltaics and, more broadly, active optoelectronics.
authors.affiliation: Division of Physical Sciences and Engineering, Solar and Photovoltaics Engineering Center, King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900, Saudi Arabia.
authors.forename: Jun
authors.initials: J
authors.lastname: Pan
authors.forename: Ala'a O
authors.initials: AO
authors.lastname: El-Ballouli
authors.forename: Lisa
authors.initials: L
authors.lastname: Rollny
authors.forename: Oleksandr
authors.initials: O
authors.lastname: Voznyy
authors.forename: Victor M
authors.initials: VM
authors.lastname: Burlakov
authors.forename: Alain
authors.initials: A
authors.lastname: Goriely
authors.forename: Edward H
authors.initials: EH
authors.lastname: Sargent
authors.forename: Osman M
authors.initials: OM
authors.lastname: Bakr