Parameswar Hari - Oxley College of Health & Natural Sciences

Parameswar Hari

A new way to measure nanostructured materials

young man with shoulder-length hair and short beard wearing a dark blazer, white shirt and striped tie
Grant Mayberry

Grant Mayberry is a rising senior, majoring in engineering physics with a focus on materials process. He was thrilled to learn recently that a paper he wrote based on his research on nanomaterials has been published in the Journal of Undergraduate Reports in Physics (JURP).

In this paper, Mayberry outlines an experimental and mathematical model for determining the dielectric properties of nanostructured materials and provides data for zinc oxide (ZnO) nanoparticles. “The dielectric properties of any material are important for understanding how that substance might behave in an electrical or optical context,” explained Mayberry.

But nanostructured materials differ from everyday materials because they are literally structured at the nanoscale (the nanoparticles Mayberry and his co-researchers use are ~21.9nm spheres of ZnO). According to Mayberry, “This is an important material for use in the newest generation of solar technology, so it’s crucial that we know its electrical and optical behavior.”

The method Mayberry proposes in his JURP paper has several key advantages: The material’s dielectric properties can be determined over a wide range of electrical and optical frequencies, only a relatively small volume of powder is required and the material’s behavior in liquids can be studied.

Labwork and mentorship

a scientific workstation with a computer, monitor, many wires and other pieces of technological equipment
Mayberry’s workstation at TU, including an impedance analyzer, computer and dielectric cell used to take measurements (some impedance spectra can be seen on the screen)

The work that formed the basis of Mayberry’s publication was conducted in the Semiconductor Characterization Laboratory run by Professor of Physics Parameswar Hari.

“Dr. Hari has been an excellent advisor and my research has greatly benefited from our discussions,” Mayberry commented. “He is always available to guide my inquiries, but he also gives me the freedom to pursue a variety of facets and to work at my own pace. Thanks to Dr. Hari’s guidance, I have learned so much more in his lab than what I published in the JURP.”

For his part, Hari is equally enthusiastic about his student’s qualities as a student and researcher: “Grant is outstanding. He is highly motivated, and his success is mainly due to his strong motivation to learn and improve his knowledge. I strongly feel that he will be successful in any area he chooses. He has an excellent work ethic and it is not a surprise that he was able to publish a paper on nanomaterials.”

Continuing to learn and excel

Between his junior and senior years, Mayberry is spending the summer furthering his knowledge and skills at Georgia Tech, thanks to support from a Research for Undergraduates summer fellowship from the National Science Foundation. He is currently working in Professor Zhigang Jiang’s research group, helping to test the properties of hexagonal-Boron-Nitride (hBN) for neutron radiation shielding and detection in space, as well as studying current distributions in graphene using computer simulations.

As he looks to life after graduation from TU, Mayberry aspires to continuing on to graduate-level studies in physics. “My ultimate goal is to become a physics professor,” he remarked, “so that I can give students the same opportunities I enjoyed and share with them the mathematical elegance and philosophical nature of the field of physics that I find so exciting.”

group of eight young people standing in two rows of four people, each person holding a certificate in front of themselves
Presentation winners of the TU Research Colloquium 2022 — Mayberry (front row, second from the right) placed third presenting the research published in JURP

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Improving the efficiency and lowering the environmental impact of solar cells

An article published by Professor of Physics Parameswar Hari and his former graduate student Amrit Kaphle (PhD ’19) has been selected for the RSC Advances 10th-anniversary collection focused on solar energy. At the same time, another of Hari’s peer-reviewed papers, written with his current doctoral student Rusiri Rathnasekara, has received the distinction of being featured on the cover of the May 2021 issue of Journal of Materials Research.

black and white electron microscope image of nanoribbons
Scanning electron microscope (SEM) image of nanoribbons

These publications are the results of work Hari and his co-investigators have been conducting for nearly eight years. Their endeavors are aimed at addressing two of the major drawbacks of solar cells. First, such cells are composed of 95% silicon, which is fabricated using a high-energy process that has a heavy carbon footprint. Second, the best silicon solar cells are only 24% efficient. In order to promote the widespread use of solar technology, Hari explained, two things must happen: the cost of production must decrease significantly and the method of manufacturing must be carbon neutral.

High-efficiency solar cells: cost effective and carbon neutral

To achieve these goals, said Hari, “the focus of our investigations has been on fabricating high-efficiency solar cells using novel materials that are both abundant in nature and cost effective.” One such material Hari and his co-investigators have explored and tested is nano-structured zinc oxide (ZnO). Specifically, they have been analyzing mechanisms for controlling the efficiency of thin-film ZnO suitable for solar cell applications.

black and white image of cross-sectional view of nanorods
Scanning electron microscope (SEM) image of nanorods (cross-sectional view)

In the RSC Advances article — Enhancement in the performance of nanostructured CuO-ZnO solar cells by band alignment – Hari and his team reported on their discovery that by carefully “doping” ZnO with cobalt, the light absorption in thin-film zinc oxide could be improved. “This will ultimately enhance the efficiency of solar cells made of this material,” Hari noted.

The researchers’ contribution to the Journal of Materials ResearchImpedance spectroscopy of nanostructured ZnO morphologies – documents the testing of a new electrode made of the thin-film material in a dye-sensitized solar cell. Using impedance spectroscopy in the Oklahoma Photovoltaic Research Institute lab at The University of Tulsa, Hari and Rathnasekara found a significant improvement in the performance of this solar cell.

As the world shifts away from fossil fuels and interest grows in solar energy and other renewable resources, Hari and his colleagues’ research becomes ever more important. Added to that, Hari noted, the U.S. military has become interested in the ability of cost-effective thin-film solar cells to replace expensive solar cells currently used in drones and other aircraft.

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