Perovskite materials have garnered much attention over the past few years due to their excellent power conversion efficiency (PCE) in solar cells, outstanding quantum yield (QY) in LEDs, and overall low production cost. The major bottleneck for commercialization, however, is low stability, especially towards moisture and polar solvents. Our strategy utilizes non-linear block copolymers with distinct polymer blocks as nanoreactors to simultaneously create nanostructured materials with precisely tuned dimensions as well as enhanced stability that cannot be achieved via conventional ligand assisted methods. In our research, we have successfully synthesized Cs-based perovskite QDs with tailored dimensions that are intimately and permanently tethered with hydrophobic polystyrene by capitalizing on rationally designed star-like block copolymer poly(acrylic acid)-b-polystyrene (PAA-b-PS) as nanoreactors. By utilizing ATRP to synthesize low PDI PAA blocks (which can coordinate with perovskite precursors), we accurately control the size of the perovskite QDs, thus allowing strict control over light harvesting and emission at desired wavelengths in the visible region. Our results show that FWHM of PS-capped CsPbBr3 QD photoluminescence (PL) was as low as 17.7 nm. Also by post anion exchange we were able to control the PL peak position from 400 nm to 700 nm. Intriguingly, each PS-capped perovskite QD, for the first time, has a separate protective shell that can be precisely tailored to any desired length/thickness. The permanently tethered PS protective shell on the perovskite QD surface showed striking improvements in terms of stability. PS-capped CsPbBr3 QD’s QY, PL peak position, and FWHM in solution (toluene) was maintained for more than 2 months without any change. Also PS-capped CsPbBr3 QDs showed up to 20x increase in water stability compared to conventional ligand-capped CsPbBr3 QDs.

All inorganic perovskite nanocrystals with precisely controlled optical properties and enhanced stability via non-linear amphiphilic block copolymers

256th National Meeting (2018)

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