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Halide Perovskite Semiconductor

Lab SIGMA focuses on understanding interface phenomena in halide perovskites and developing scalable tailoring strategies for functional interfaces for high performance devices.

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Lab SIGMA focuses on using advanced characterization tools to probe nanoscale structure-function correlation in  semiconductor materials and devices.

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Combintorial Solution Synthesis

Lab SIGMA focuses on developing automated solution deposition systems for fabricating inorganic materials libraries for high-throughput materials screening.



Synchrotron X-ray Characterization

Halide Perovskite Semiconductor

    Halide perovskites (HPs) emerges as a new family of semiconductor materials that are promising for the use in functional electronics. The most standard HPs have a three-dimensional (3D) crystal structure with chemical formula of ABX3, where A is a monovalent organic cation (e.g. CH3NH3, HC(CH2)2, Cs), B is a divalent metal cation (e.g. Pb, Sn, Ge), and X is a halide anion (e.g. I, Br, Cl). The HP family has later embraced many new perovskite ‘‘members’’ with reduced crystallographic dimensionalities, such as 2D Ruddlesden-Popper phase and 2D Dion-Jacobson, as well as numerous pseudo-members. Such structure and composition versatility has led to a fascinating materials platform for exploring electronic, optical, magnetic, ionic, mechanical properties as well as their couplings, demonstrating potentials for numerous energy and information applications.


    Our research aims to gain an in-depth understanding of key interfaces such as grain boundaries and heterophase interfaces in HP thin films regarding their beneficial or detrimental roles in device functions. We are also reaching the vast hybrid organic-inorganic chemistry involved in the solution processing and crystallization/transformation of HPs to engineering microstructures in a deterministic manner. 

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Synchrotron X-ray Characterization


   Since the early development of storage-ring-accelerator-based synchrotrons declared its independence out of parasitic phase with high-energy physics facilities, the gigantic X-ray source has evolved into one of the mainstream scientific tools essential in tackling challenging scientific problems, in particular leading to transformational levels of insights to our ability to explore, understand and create a variety of new materials which would bring about enormous technological and societal impacts in engineered structures, modern electronics, sustained energy sources and a host of other applications. The advances in materials discoveries enabled by versatile X-ray techniques derived from the three major pillar categories of scattering, spectroscopy and microscopy have been tremendous and ever-lasting, concertedly propagated both by emergence of new fundamental ways to understand the interaction of X-rays with a variety of materials and by the evolution of light-sources themselves. 

     Our research focuses on using highly focused synchrotron X-rays down to submicron and nanoscale to acquire more sampling in greater detail of samples in shorter time to interrogate existing and emerging semiconductor materials. Structural, compositional and electronic inhomogeneity across the sample will be efficiently mapped and recorded. Subtle or even hidden correlation between different imaging modalities may well be unraveled through high throughput tests and deep-learning assisted image recognition/mining. Significantly higher coherent flux facilitated with rapid advances in data analysis and computation will make X-ray microscopy like ptychographic methods far more accessible and efficient in the near future, which could put forward high-spatiotemporal-resolution 4D (x, y, z, t) characterizations of semiconductors in realistic operation environments or conditions.

Combintorial Solution Synthesis

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    Combinatorial synthesis is a high-throughput method for materials screening and discovery. Instead of preparing and examining a single material, families or 'libraries' of new substances are simultaneously fabricated and screened for desired physical properties and device applications. The below figure shows a schematic sample library with 'vivid' compositions. 

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   Our research relies on the solution-processiblity of emerging semiconductors, and aims to develop unprecedented platform for rapid screening of new promising semiconductors. This approach will be coupled with the the development of combinatorial characterization based on tailored high-spatiotemporal-resolution characterization techniques such as synchotrotron and microscopy. We also collaborate with computational materials scientists closely to boost the efficiency of materials screening and discovery processes.

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