(7gp) Aerosol Synthesis of Materials for Sunlight Harvesting Applications

Research abstract:

With the increase in the greenhouse gas emission from conventional energy sources and concerns about global warming, the demand for renewable energy is growing rapidly. Sunlight is one of the cheapest and abundant sources of energy available in nature. However, the high cost of the most efficient and commercialized silicon solar cells makes it challenging to take full advantage of the freely available sunlight. Therefore, it is important to develop cheap, efficient, and stable devices to harvest solar energy. My research is focused on the synthesis of materials via novel aerosol generation techniques (at Aerosol and Air Quality Research Laboratory), advanced material characterization (at Argonne National Laboratory) and their application in sunlight harvesting.

Aerosol-based techniques are simple, scalable, and operate at atmospheric pressure. Moreover, they can be operated continuously and allow precise control of material properties (size, morphology, crystal structure, composition), which are the challenges for earlier solution-based techniques. I will discuss one such aerosol-based technique, electrohydrodynamic atomization (i.e., electrospray), for fabricating materials with desired properties for efficient sunlight harvesting. Specific examples in brief are:

1. Directed-assembly of Thylakoid membrane: Thylakoid membrane contains light harvesting complexes, Photosystem (PS) I and II. This project focuses on re-engineering the naturally occurring photosynthetic thylakoid membrane using electrospray to fabricate an artificial photo-electrochemical cell for solar energy conversion.

• Kavadiya, S., Chadha, T. S., Liu, H., Shah, V. B., Blankenship, R. E., and Biswas, P., “Directed assembly of the thylakoid membrane on nanostructured TiO₂ for a photo-electrochemical cell”, Nanoscale, 8, 1868, 2016

2. Improving stability of perovskite solar cells under humid environment: Recently developed highly efficient and low-cost perovskite (CH₃NH₃PbI₃) solar cells (PSCs) are vulnerable in ambient humid environment. Our electrospray technique makes stable PSCs by controlling the rate of perovskite formation precisely and under ambient conditions. The perovskite film fabricated using electrospray is highly smooth and moisture-resistant.

• Kavadiya, S., Niedzwiedzki, D. M., Huang, S., and Biswas, P., “Electrospray-assisted Fabrication of Highly Stable and Efficient Perovskite Solar Cells at Ambient Conditions”, Advanced Energy Materials, doi: 10.1002/aenm.201700210, 2017
• Carvalho, B. A. de*, Kavadiya, S.*, Huang, S., Niedzwiedzki, D. M., and Biswas, P., “Highly stable perovskite solar cells fabricated under humid ambient conditions”, IEEE Journal of Photovoltaics, 7, 532, 2017 (*equal contribution)

3. Crumpling of 2D graphene oxide (GO) sheet: Graphene oxide has numerous applications in almost every field, because of its remarkable properties. However, the 2D sheets tend to restack and lose the surface area, hence hinder their efficient utilization. Using electrospray technique, we crumple the 2D sheets into stable nanoscale 3D structure at room temperature, preserving the surface area to a significant extent. We also synthesize composite materials with CGO and utilize these nanomaterials for efficient conversion of carbon dioxide to useful fuels (CO, CH₄) and sensing application.

• Kavadiya, S., Raliya, R., Schrock, M., and Biswas, P., “Crumpling of graphene oxide through evaporative confinement in nano-droplets produced by electro-hydrodynamic aerosolization”, Journal of Nanoparticle Research, 19: 43, 2017
• Lin, L-Y., Nie, Y., Kavadiya, S., and Biswas, P., “N-doped reduced graphene oxide promoted nano TiO₂ as a bifunctional adsorbent/photocatalyst for CO₂ photoreduction: Effect of N species", Chemical Engineering Journal, 316, 449, 2017

Overall, based on PhD research work, I gained experience in material synthesis, advance level characterization, and device fabrication. For the above-mentioned work, I received a doctoral student research award from the Department of Energy, Environmental and Chemical Engineering at Washington University in St. Louis.

Research interest:

In future, as a faculty, I would like to continue applying aerosol-based methods to synthesize materials for various applications. I believe that aerosol-based techniques have large potential to prepare materials with desired properties (self-assembled structure in the first project, moisture-resistance smooth film in the second project and crumpled GO structure in the third project). Furthermore, aerosol-based techniques are scalable for large-scale production and efficiently use the precursor material, reducing material loss significantly. I will also try to advance the technique I develop from lab-scale to larger-scale for commercial use. I will describe my detail research plan during the poster session. Below are few proposed future research projects in brief:

i. Hydrophobic crumpled graphene-perovskite composite: I have experience with synthesis and application of both graphene-based composite materials and perovskite. Furthermore, aerosol based techniques are exceptionally good in synthesizing crumpled graphene-based composite materials. As mentioned earlier, perovskite are prone to moisture. The aim is to cover the perovskite with waterproof graphene sheet and make the perovskite hydrophobic. My expertise on aerosol-based synthesis of crumple graphene composites will be unique to execute this project.

ii. Large area perovskite solar cells: I have successfully fabricated stable PSCs using electrospray technique at ambient condition. It is very important to make efficient PSCs on larger scale. Other than the excellence of aerosol-based techniques in precisely controlling the material properties, these techniques are scalable for commercial application. My aim for this project is to scale up the electrospray deposition system to make large area stable perovskite solar cells under ambient condition.

Finally, I will combine the synthesis with the advanced characterization techniques through my collaboration at Argonne National Lab, to understand their formation mechanism and specific properties. Other than experimental characterization of the materials, I believe that the use of quantum mechanical modeling provides a fair idea about the material properties at atomic scale and optimizes the experimental efforts. Therefore, I foresee myself collaborating closely with computational groups and/or having a computational component in my own laboratory.

Teaching Interests:

Besides doing research work, I have also been interested in teaching. Through teaching, I want to ignite curiosity in students, teach them to think critically and develop essential skills. I started gaining teaching experience by doing teaching assistantship (TA) since my undergraduate education. During the past years in my PhD, I have TAed courses such as Engineering Analysis of Chemical Systems, Advanced thermodynamics and Material science, in which the first two included classroom teaching, organizing homework and exam material. A challenge to me in teaching is to teach undergraduate class from the base level while maintaining the flow. Therefore, I always be careful in choosing examples and try to connect the scientific principles to the daily life examples. I am enrolled in teaching citation program at the Washington University teaching center, which is focused on improving teaching skills through workshops, developing new teaching methods, applying them in class and coming up with the teaching philosophy. In future, as a faculty, I would like to teach fundamental courses on Chemical Processes (consisting mass, energy and momentum balance), Aerosol Science, and Material Science and Engineering.

Lastly, I also mentored three undergraduate students with very diverse background in their summer intern research projects in our lab and have journal publications with two of them. I am always enthusiastic to teach them the importance, capabilities and useful outcome from doing novel research work. I see myself getting better in mentoring students each year. I will continue to develop my teaching skills in both classroom teaching and in-person student mentorship.