RII Track-4 - EPSCoR Research Fellow: Matthew White, University of Vermont

RII-Track 4: Digital Alloy Contact Layers for Solar Cells:
EPSCoR Research Fellow: Matthew White

Assistant Professor Matthew White of the UVM Department of Physics and Materials Science Program
Dr. Matthew White, Assistant Professor of Chemistry at the University of Vermont received an NSF RII Track-4 award for his research titled "Digital Alloy Contact Layers for Solar Cells". The work pertains to increasing the efficiency of solar energy systems which is critical to meeting the nation's future energy needs. The project seeks to address the fundamental problem that a single material is often called upon to perform multiple functions within a solar cell, demanding varying properties within extremely thin films. For this project, the PI and a graduate student will work with the National Renewable Energy Laboratory (NREL) to study the fabrication and characterization of specific thin films and their potential application in solar cells. By controlling the material composition during the fabrication of these films with sub-nanometer resolution, it will be possible to maximize the energy-harvesting efficiency and minimize losses that occur in several solar cell technologies, a critical step in securing our energy future. This proof-of-concept work will build a solid foundation for future collaborative research between the PI's home institution (University of Vermont), the extended renewable energy research community in Vermont, and NREL.

1. Larsen, A., Dahal, E., Paluba, J., Cianciulli, K., Isenhart, B., Arnold, M., Du, B., Jiang, Y., and White, M. S. “Nonlinear Impedance Spectroscopy of Organic MIS Capacitors and Planar Heterojunction Diodes” Organic Electronics 62, (2018): 660–666. doi:10.1016/j.orgel.2018.07.003
During the summer of 2018, Assistant Professor Matthew White of the UVM Department of Physics and Materials Science Program and one graduate research assistant traveled to Golden Colorado to spend three months working with global leaders in perovskite solar cells at the National Renewable Energy Laboratory (NREL). Three UVM undergraduate physics majors joined them, with travel supported by the UVM Clean Energy Fund. The team used Pulsed Laser Deposition (PLD) to construct digital alloy oxide films with precise energy band and doping gradient control. These digital alloys were used as electron-selective contact layers for perovskite solar cells to simultaneously maximize the charge collection efficiency and prevent carrier recombination, improving both the short circuit current and open circuit voltage, as seen in the solar cell J-V curves below. Doing so requires precise, sub-monolayer control of both isovalent substituent (Mg) and dopant (Ga) concentration in an intrinsic ZnO host matrix. PLD offers an ideal tool for digital alloy fabrication as the laser pulses occur on the order of 1 to 10 per second, each depositing a small fraction of a monolayer of material. By switching targets between laser pulses, we fabricated such digital alloy gradient thin films. The tools necessary to fabricate and characterize such advanced nanomaterials are only available at NREL. A publication entitled “Digital alloy contact layers for solar cells” is currently in preparation summarizing the results of our summer research. An additional publication entitled “Nonlinear impedance spectroscopy of organic MIS capacitors and planar heterojunction diodes”, based on our preparatory work during spring 2018, was published in Organic Electronics.[1] The work was also presented at the Materials Research Society Fall 2018 meeting in Boston, MA.
Award Abstract #1738575