Our research activities are grouped into 2 categories with the central goal to enhance the stability and performance of perovskite-based tandem solar cells, including Si/perovskite, organic/perovskite, and all-perovskite tandem cells. 

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Characterization: Our main strength is the characterization of solar cells, where we focus foremost on a quantitative analysis of ionic degradation loss mechanisms and understanding the mobile ion density evaluation during device aging, which determines the stability of perovskite cells. To do this, we use various innovative electro-optical measurements, especially "fast-hysteresis" (scan-rate dependent) JV characterization, as well as charge extraction and capacitance-based measurements.

 

More broadly, we aim to decouple various recombination loss mechanisms under different environmental stressors using a range of electro-optical measurements, such as PL spectroscopy.

 

Recently, we also tried to utilize AI and machine learning to assist us in the interpretation.

 

By gaining a better understanding of the underlying degradation mechanisms, we try to be able to quickly identify perovskite compositions and devices that will likely operate over a long period of time.

 

Recently, we also investigate the hot carrier extraction from the perovskite, which may 1 day allow us to overcome the detailed balance efficiency limit of single junctions (>33.7%)

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Device development:

 

Apart from characterization, we focus on wide-bandgap perovskites, which typically suffer from halide segregation leading to instabilities. However, our recent perovskite formulations based on pure-iodine perovskite now lead to greatly improved operational lifetimes with excellent phase stabilities.

 

Another central aspect of our research is the advancement of functional transport layers to improve extraction and minimize interfacial recombination losses. For example, we recently implemented highly stable self-assembled monolayers that can overcome the long-standing challenge of reverse bias breakdown in perovskite PV.

 

In addition, to compositional and transport engineering, we develop ultra-light flexible perovskite photovoltaics, with the long-term goal to develop space PV to power satellites or future space missions.Moreover, we aim to utilize such flexible perovskite solar cells in sensor applications such as IoT sensors, as well as smart wearable health sensors, in collaboration with Prof. Ni Zhao from EE.

 

Beyond solar cells, we also utilize perovskite for detector applications, in particular Xray detectors, where perovskites have unique advantages.

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Finally, to advance organic/perovskite ultra-thin tandem solar cells, we study loss mechanisms of low-bandgap organic semiconductors and associated solar cells with state-of-the-art performances.