Seminar Schedule – Spring 2021
Tuesday, April 13, 2021
Time: 3:30pm – 5:00pm
This seminar will be held virtually via Zoom in email announcement
Design, Fabrication, and Characterization of Engineering Materials for Energy Devices
Dr. Nick Rolston
Postdoctoral Scholar
Mechanical Engineering, Stanford University
Abstract: Photovoltaic (PV) devices and batteries are essential for the transition to renewable energy. These technologies often incorporate layered thin film structures, for which the understanding of mechanical properties is crucial to designing durable and cyclable devices. Metal halide perovskites are the leading class of materials for next-generation thin film PV based on their high power conversion efficiencies on lab-scale devices, but limitations in device stability have challenged the path to commercialization. Similarly, the excellent energy and power densities of lithium batteries have enabled widespread usage in portable electronic devices and electric vehicles; however, the technology is plagued by short lifetimes that limits potential for grid-scale storage. As a result, lithium batteries experience similar limitations in device stability that have challenged the commercialization of perovskite PV—which I discovered are the most mechanically fragile class of PV ever tested in comparison to organic, copper indium gallium selenide, and silicon cells. Additionally, I showed that perovskites accumulate significant tensile film stresses during processing—comparable to the yield strength of copper—from their large thermal expansion coefficient compared to commonly used glass or Si substrates. Lithium batteries also accumulate large film stresses in operation from significant volumetric changes during cycling. Since the mechanical driving force for damage scales as the square of the film stress, σ, the mechanical fragility of energy materials leads to increased device instability and results in scale-up and cyclability challenges. Thin film energy materials often incorporate flexible substrates, and device layers are subjected to additional mechanical stress from externally applied stretching or flexing. Designing reliable energy materials with longer operational lifetimes is therefore essential for the long-term viability of the technologies.
For further information, please contact Dr. Stelios Kyriakides at skk@mail.utexas.edu or (512) 471-4167.
