1 research outputs found
Shape‑, Size‑, and Composition-Controlled Thallium Lead Halide Perovskite Nanowires and Nanocrystals with Tunable Band Gaps
Perovskite
nanocrystals have shown themselves to be useful for both absorption-
and emission-based applications, including solar cells, photodetectors,
and LEDs. Here we present a new class of size-, composition-, and
shape-tunable nanocrystals made from Tl<sub>3</sub>PbX<sub>5</sub> (X= Cl, Br, I). These can be synthesized via colloidal methods to
produce faceted spheroidal nanocrystals, and perovskite TlPbI<sub>3</sub> nanowires. Crystal structures for the orthorhombic and tetragonal
phase materials, for both pure and mixed halide species, are compared
to the literature and also calculated from first-principles in VASP.
We show the ability to tune the band gap by halide substitution to
create materials that can absorb strongly between 250 and 450 nm.
In addition, we show evidence of the confinement effect in pure halide
Tl<sub>3</sub>PbBr<sub>5</sub> nanocrystals suggesting size-tuning
is possible as well. By tuning the band gap we can create materials
with specific absorption spectra suitable for photodetection that
display conduction and photoresponse properties similar to previously
observed perovskite nanocrystals. We also observe weak emission consistent
with indirect band-gap materials. Finally, we are able to demonstrate
shape control in these materials, to give some insight into observable
phase changes with varying reaction conditions, and to demonstrate
the utility of the TlPbI<sub>3</sub> perovskite nanowires as wide-band-gap
photoconductors. These novel perovskite nanocrystalline materials
can be expected to find applications in photodetectors, X-ray detectors,
and piezoelectrics