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To meet the energy demands of modern times using renewable sources, it's crucial to develop
photovoltaic and optoelectronic devices with high efficiency and low energy consumption. The success
of these devices relies on two main factors: macroscopic performance and durability. These factors, in
turn, are governed by the microscopic structural, chemical, and functional properties that are affected
by defects, carrier transport, and chemical reactions under external stimuli such as light, bias, and
ambient conditions.1 Therefore, understanding the microstructure-function-performance relationships
in these devices is paramount.
2 However, it's currently very challenging to correlate the microstructure
with the spatio-temporal variability in composition and performance of the photoactive layer inside
working optoelectronic devices such as photovoltaics, photodetectors, and light emitting diodes. This
is because of the complex architecture of the devices where the photoactive layer is sandwiched between
multiple transport layers and electrodes.
To tackle these challenges, I am developing the Correlative Smart Microscopy technique, which
integrates smart data processing algorithms, smart control of material chemistry and standard optical
and electron microscopes. Within this framework, I have introduced Correlation Clustering Imaging
(CLIM), a novel noninvasive method that utilizes photoluminescence fluctuations to reveal contrasts
associated with defect dynamics in semiconductor materials. CLIM images of perovskite thin films
show one-to-one matching with the grains in SEM images captured at the same locations. Particularly
noteworthy is the application of CLIM to high-efficiency photovoltaic devices, uncovering previously
unnoticed photoluminescence intensity fluctuations that strongly depend on the operational regime of
the device. Statistical analysis of these intensity fluctuations provides insights into the type of
metastable defects responsible for fluctuating non-radiative recombination processes.3
The insights gained from CLIM contribute to a deeper understanding of device efficiency, structure,
and degradation, which are crucial for the rational engineering of the next generation of devices. With
its broad applicability, requiring only a standard wide-field microscope and our user-friendly algorithm,
CLIM emerges as an important new tool for material chemists, engineers, and device scientists. |