2 research outputs found
Growth and Characterization of PDMS-Stamped Halide Perovskite Single Microcrystals
Recently, halide perovskites have
attracted considerable attention
for optoelectronic applications, but further progress in this field
requires a thorough understanding of the fundamental properties of
these materials. Studying perovskites in their single-crystalline
form provides a model system for building such an understanding. In
this work, a simple solution-processed method combined with PDMS (polydimethylsiloxane)
stamping was used to prepare thin single microcrystals of halide perovskites.
The method is general for a broad array of materials including CH<sub>3</sub>NH<sub>3</sub>PbBr<sub>3</sub>, CH<sub>3</sub>NH<sub>3</sub>PbCl<sub>3</sub>, CH<sub>3</sub>NH<sub>3</sub>Pb(Br<sub>0.5</sub>Cl<sub>0.5</sub>)<sub>3</sub>, CH<sub>3</sub>NH<sub>3</sub>Pb(Br<sub>0.75</sub>Cl<sub>0.25</sub>)<sub>3</sub>, CsPbBr<sub>3</sub>, Cs<sub>3</sub>Bi<sub>2</sub>Br<sub>9</sub>, and Cs<sub>3</sub>Bi<sub>2</sub>I<sub>9</sub>. Electron backscatter diffraction (EBSD) was used to
investigate the microstructure of the crystals. In order to characterize
the microcrystals of CH<sub>3</sub>NH<sub>3</sub>PbBr<sub>3</sub> electrically,
the crystals were grown on prefabricated electrodes creating single-crystal
devices contacted from the back. This back-contacted platform circumvents
the incompatibility between halide perovskites and the aqueous chemistry
used in standard microfabriation processes. It also allows <i>in situ</i> characterization of the perovskite crystal while
it operates as a microscopic solar cell
Perovskite Nanowire Extrusion
The defect tolerance
of halide perovskite materials has led to
efficient optoelectronic devices based on thin-film geometries with
unprecedented speed. Moreover, it has motivated research on perovskite
nanowires because surface recombination continues to be a major obstacle
in realizing efficient nanowire devices. Recently, ordered vertical
arrays of perovskite nanowires have been realized, which can benefit
from nanophotonic design strategies allowing precise control over
light propagation, absorption, and emission. An anodized aluminum
oxide template is used to confine the crystallization process, either
in the solution or in the vapor phase. This approach, however, results
in an unavoidable drawback: only nanowires embedded inside the AAO
are obtainable, since the AAO cannot be etched selectively. The requirement
for a support matrix originates from the intrinsic difficulty of controlling
precise placement, sizes, and shapes of free-standing nanostructures
during crystallization, especially in solution. Here we introduce
a method to fabricate free-standing solution-based vertical nanowires
with arbitrary dimensions. Our scheme also utilizes AAO; however,
in contrast to embedding the perovskite inside the matrix, we apply
a pressure gradient to extrude the solution from the free-standing
templates. The exit profile of the template is subsequently translated
into the final semiconductor geometry. The free-standing nanowires
are single crystalline and show a PLQY up to ∼29%. In principle,
this rapid method is not limited to nanowires but can be extended
to uniform and ordered high PLQY single crystalline perovskite nanostructures
of different shapes and sizes by fabricating additional masking layers
or using specifically shaped nanopore endings