4 research outputs found
Mapping the Pathways of Photo-induced Ion Migration in Organic-inorganic Hybrid Halide Perovskites
Organic-inorganic hybrid perovskites (OIHPs) exhibiting exceptional
photovoltaic and optoelectronic properties are of fundamental and practical
interest, owing to their tunability and low manufacturing cost. For practical
applications, however, challenges such as material instability and the
photocurrent hysteresis occurring in perovskite solar cells under light
exposure need to be understood and addressed. While extensive investigations
have suggested that ion migration is a plausible origin of these detrimental
effects, detailed understanding of the ion migration pathways remains elusive.
Here, we report the characterization of photo-induced ion migration in OIHPs
using \textit{in situ} laser illumination inside a scanning electron
microscope, coupled with secondary electron imaging, energy-dispersive X-ray
spectroscopy and cathodoluminescence with varying primary electron energies.
Using methylammonium lead iodide (MAPbI), formamidinium lead iodide
(FAPbI) and hybrid formamidinium-methylammonium lead iodide as model
systems, we observed photo-induced long-range migration of halide ions over
hundreds of micrometers and elucidated the transport pathways of various ions
both near the surface and inside the bulk of the OIHPs, including a surprising
finding of the vertical migration of lead ions. Our study provides insights
into ion migration processes in OIHPs that can aid OIHP material design and
processing in future applications
Imaging Strain-Localized Single-Photon Emitters in Layered GaSe below the Diffraction Limit
Nanoscale strain control of exciton funneling is an increasingly critical
tool for the scalable production of single photon emitters (SPEs) in
two-dimensional materials. However, conventional far-field optical microscopies
remain constrained in spatial resolution by the diffraction limit and thus can
only provide a limited description of nanoscale strain localization of SPEs.
Here, we quantify the effects of nanoscale heterogeneous strain on the energy
and brightness of GaSe SPEs on nanopillars with correlative
cathodoluminescence, photoluminescence, and atomic force microscopies supported
by density functional theory simulations. We report the strain-localized SPEs
have a broad range of emission wavelengths from 620 nm to 900 nm. We reveal
substantial strain-controlled SPE wavelength tunability over a ~ 100 nm
spectral range and two-orders of magnitude enhancement in the SPE brightness at
the pillar center due to Type-I exciton funneling. In addition, we show that
radiative biexciton cascade processes contribute to the observed CL photon
superbunching. Also, the measured GaSe SPE photophysics after electron beam
exposure shows the excellent stability of these SPEs. We anticipate this
insight into nanoscale strain control of two-dimensional SPEs will guide the
development of truly deterministic quantum photonics
Mapping the pathways of photo-induced ion migration in organic-inorganic hybrid halide perovskites
Ion migration is a plausible origin of material instability and photocurrent hysteresis in perovskite solar cells. Here, authors characterize photo-induced ion migration in perovskites by in situ laser illumination inside scanning electron microscope and observe long-range migration of halide ions
Recommended from our members
Mapping the pathways of photo-induced ion migration in organic-inorganic hybrid halide perovskites
Organic-inorganic hybrid perovskites exhibiting exceptional photovoltaic and optoelectronic properties are of fundamental and practical interest, owing to their tunability and low manufacturing cost. For practical applications, however, challenges such as material instability and the photocurrent hysteresis occurring in perovskite solar cells under light exposure need to be understood and addressed. While extensive investigations have suggested that ion migration is a plausible origin of these detrimental effects, detailed understanding of the ion migration pathways remains elusive. Here, we report the characterization of photo-induced ion migration in perovskites using in situ laser illumination inside a scanning electron microscope, coupled with secondary electron imaging, energy-dispersive X-ray spectroscopy and cathodoluminescence with varying primary electron energies. Using methylammonium lead iodide and formamidinium lead iodide as model systems, we observed photo-induced long-range migration of halide ions over hundreds of micrometers and elucidated the transport pathways of various ions both near the surface and inside the bulk of the samples, including a surprising finding of the vertical migration of lead ions. Our study provides insights into ion migration processes in perovskites that can aid perovskite material design and processing in future applications